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**Motoring a Sailboat**
Published 2023-04-25; Updated 2024-07-05![](motoring.jpg width=555px attrib="Yachting Monthly" attrib-url="https://www.yachtingmonthly.com/sailing-skills/saving-fuel-when-under-engine-for-greater-efficiency-85094")
Keelboats often have motors to aid in docking or making way in poor sailing conditions. This article focuses on maneuvering keelboats with inboard engines.
Motoring is also called auxilliary propulsion for a sailboat, since the primary means of propulsion is of course sailing. It is prudent to keep in mind that motoring is auxilliary. I personally wouldn't leave the dock in any boat where I wasn't confident I could also return without a motor.
The key idea of motoring a medium length keelboat is that the helmsperson must manipulate several sources of force and momentum in concert to achieve the desired motion. Sailboats under power do not drive like cars. They don't even drive like busses, which are closer to the length and mass involved. Putting the transmission in gear and steering wide turns works for covering distance in open areas, but is not how to maneuver a boat within a marina.
The factors involved are the wind and current, the fore-aft thrust of the propeller, the drag of the rudder, the prop wash redirection of the rudder, the prop walk, the intertia of the boat, and the linear and angular momentum of the hull. These can be confusing and confounding when first encountered, but become essential tools once understood.
For example, it is a common situation to intentionally be in forward gear and with the wheel steering to hard to starboard, while actually moving backwards and rotating to port. In fact, this is part of the back and fill maneuver for turning significant amounts in place within a fairway.
Engine maintenance and mooring (docking and anchoring) techniques are covered in separate articles instead of this one. Also not covered in this article are techniques specific smaller boats with outboard motors. These boats operate much like slightly awkward motor launches under power and the techniques described here are not necessary. That is, except for having to steer with both the engine and tiller, smaller boats are relatively straightforward to handle under power (once your engine starts). In a pinch, smaller boats are also amenable to paddling, sculling with the rudder, and simply being pushed or pulled by hand off obstructions in a marina.
I focus here on monohull sailboats with a single drive. Large sailboats with twin props and catamarans handle differently and have additional options and concerns.
When propelled by a motor, a boat must follow powerboat navigation regulations. These apply when motorsailing as well as when the sails are completely down. The most significant change is that it must give way to sailboats under sail and other unpowered craft.
If the sails are up and engine is running but not in gear, for example, as a backup or to charge batteries, then the boat technically is under sail propusion.
However, the boat with the engine running should still give way to other sailboats in practice. It has immediate access to increased maneuverability from the engine, which is the intent of the navigation rules. Also, when another sailboat hears the engine running, they will assume that the boat with the engine is making way under power and expect it to keep clear.
![ ](lights.jpg width=250px attrib-url="https://www.westmarine.com/west-advisor/Navigation-Light-Rules.html" attrib="West Marine") At night or in poor visibility a sailboat under power must run a navigation steaming light. This is a white forward light on the mast covering 225 degrees.
On the breaker panel where the navigation lights are turned on, there will will be a switch to toggle them between "sail" and "steaming" (or "power"). Remember to change the switch back to "sail" when you stop the engine and resume sailing.
When boats meet and need to deviate from the default navigation rules or need quick emergency communication, they signal with sound signals on a horn or whistle.
Except for the anchored in fog signals, these are the same when under sail or under power. However, you are more likely to need these under power. That's because under sail, most power boats are staying clear of you, and you very are unlikely to be operating in reverse.
The signals are:
| Signal | Description | Meaning |
|---|---|---|
| ∙ | One short | "Altering course to starboard" |
| ∙∙ | Two short | "Altering course to port" |
| ∙∙∙ | Three short | "Operating in reverse" |
| ∙∙∙∙∙ | Five rapid | "I’m unsure of your intentions!", usually to avert a collision and with a measure of in panic from a small boat or anger from a large one. |
| ─── | One long | "My boat is longer than 12m and leaving the dock under power" i.e., "get out of my way, I can't turn or stop quickly" |
Technically, one should sound three short blasts whenever reversing away from a dock or mooring. However, this is usually frowned on in locations where it would disturb neighbors on the water and land. You will most often hear the reversing signal only from ferries or cargo ships. Use your judgement if there is obviously no risk of other small boats not noticing your movement.
Beware that there are special signal interpretations on the Great Lakes.
In restricted visibility, such as fog, make the following signals repeatedly:
| Signal | Description | Meaning |
|---|---|---|
| ── ∙ ∙ | One long blast followed by two short blasts every two minutes | "I'm here and under sail" |
| ── | One long blast every two minutes | "I'm here and under power" |
| ∙∙∙∙∙∙ | Rapid blasts for five seconds, every minute | "I'm at anchor" (or aground) |
When boats meet, there is a stand on vessel that is required to maintain its current course and speed, and a give way vessel that is required to keep clear. Sailors often casually refer to the stand on vessel as having "right of way", but keep in mind that it is not free to change during the passing time as then the other vessel cannot anticipate its actions.
Boats under power must give way and keep clear of boats under sail or human propulsion unless they are overtaking. That includes windsurfers, paddleboarders, and kayaks.
For boats under power, the rules are the same as for cars (in drive-on-the-right countries) and thus easy to remember:
- Go on green, change course on red or white
- Drive on the right side head on or in a restricted lane
 
 
When two boats under power meet, their interactions are generally governed by a simple observation. Where is the other boat relative to yours? If it is approaching on your forward port quarter extended a bit past the port beam, then you are on the stand-on vessel. Otherwise you are the keep-clear vessel because they're on your port side or you're overtaking (or both).
A boat approaching your port aft quarter is either within your port light or stern light arc. So, you are the stand-on vessel, because it is either approaching your port or your stern.
The tricky case is a boat approaching your starboard aft quarter, very close to 112.5 degrees off your bow (22.5 degrees aft of your beam). Depending on the exact bearing, they are either within white stern light arc and overtaking (and you are the stand on vessel), or within your green starboard light arc (and you are the give way vessel). If they are sufficiently distant and not approaching too rapidly, then altering course a bit to port might be a smart move in this situation. This makes them clearly the give way vessel that should then pass behind you.
In any situation where an oncoming boat's intentions are unclear or you believe they are not fulfilling their role under the rules, you should also:
- Sound five rapid sound signals: "Your intentions are unclear!"
- Hail, if you can access the radio quickly enough or shout clearly enough.
- Take whatever steps you believe will best avert the collision based on the situation, including making decisive and obvious course changes.
!!! Note Traffic Light Analogy It may help to think of the light signals like a traffic light. The stand-on vessel is facing the give-way vessel's green, starboard navigation light, assuming both boats are under forward propulsion. In all other cases the give-way vessel is facing the white, stern light or the red, port light on the stand-on vessel.
If you can see a green light, that's your sign to stand on. Otherwise, you should keep clear because you're approaching their port side (red light) or stern (white light). Of course, during the day you cannot see the lights. In that case you need to visualize it and determine if you are approaching within 112.5 degrees off the bow.
Of course, if the approaching vessel is on your beam, you will see both their red and green navigation lights. So, you do have to remember that them approaching on your port side means they keep clear, and them approaching on your starboard side means that you keep clear. However, if a vessel is approaching on your beam from some distance then you are probably not on a collision course.
In a fairway or channel, boats under power pass port to port unless they have signalled each other to do otherwise. This means that you drive on the starboard (right) side of a channel or fairway. This is the same as a car on a road in a non UK-convention country. It also means that while passing, both are facing a red light and it is obvious that they shouldn't turn into each other.
There are power navigation rule exceptions for special situations with working boats, especially large ones. These include active fishing boats, tugs, ferries, dredges, tow boats, cruise ships, and cargo ships. These exceptions are the same under sail.
And finally, the navigation rules (COLREGS) require everyone to avoid collisions regardless of who is supposed to be the stand on vessel:
When, from any cause, the vessel required to keep her course and speed finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision.
Motoring is obviously not the preferred way to cover long distances in a sailboat. However, firing up the engine can be necessary when fighting current, trapped without wind, or running short on daylight.
Steering in open water under power is easy and the boat mostly acts like a very large, very noisy, and very slow car. The primary considerations when covering large distances are how long it will take and how much fuel will be consumed.
Diesel engines have a particular speed, measured in revolutions per minute, RPM, at which they are most efficient. This is typically around 2000-2500 RPM for marine diesels. Engines become radically less efficient above their target speed.
On a boat, increasing the RPM can consume fuel as much as 10x faster while gaining relatively little speed, especially for a non-planing sailboat which is limited by its hull speed. The efficient speed tends to correspond to moving at 5-7 kts through the water.
When planning time and fuel consumption, the current and wind can affect the boat both positively and negatively. When they are with the boat, it can exceed its hull speed over ground and efficiently cover a larger distance.
When current and wind oppose the boat, fuel consumption will rise. Fighting a 5 kt current or strong headwind might require the engine at 4000 RPM to make headway and still only yield 2 kts of forward motion in exchange for significant fuel consumption.
Flying sails, furled sails, biminies, dodgers, and solar panels all contribute to the boat's windage. Beyond furling, there is often little that can be done to adjust this on short notice. Of course, the motor is rarely needed for long distances on a sailboat when there is wind. But with little true wind, the apparent wind when motoring will still increase fuel consumption.
As with sailing, a cross wind can also create leeway that must be compensated for when motoring. Because of its keel, a sailboat may experience less leeway and track better than a motorboat in similar conditions.
When planning a trip, factor in the likely wind and current when under power and adjust estimates accordingly.
![A Garcia 45 sailboat motorsailing](motorsail.jpg width=350px attrib="Yachting Monthly" attrib-url="https://www.yachtingmonthly.com/sailing-skills/why-motor-sailing-is-good-seamanship-72810") Motorsailing is what it sounds like, keeping the sails (typically just the main) up while motoring. The presence of the sail can act as a stabilizing force. More often, one began by sailing and engaged the motor when the breeze became too light or from an unfavorable direction. Keeping the main sail up can gain a bit of extra speed.
When motorsailing, the apparent wind will shift ahead because of the extra propulsion. The main must usually be trimmed in as if close hauled regardless of the true wind direction.
If the wind is too light, motorsailing is less efficient than simply motoring because the drag from the main exceeds the lift that it provides.
![Fisher 30 motorsailer](fisher30.jpg width=350px attrib-url="https://en.wikipedia.org/wiki/File:Fisher30.jpg" attrib="© 2008 Tonkie CC-SA 3.0") Some sailboats are specifically designed as motorsailers to frequently operate in motorsailing mode. These usually have a trawler-like design with a wide hull, flat bottom, and protected above deck pilothouse or saloon. Although aesthetically and morally offensive to many sailors, this is a practical solution for many types of cruising and regions. That includes areas with low wind or frequent bad weather. A motorsailer combines the speed, range, accomodation volume, and electrical liberties of a powerboat with the failsafe and efficiency advantages of a sailboat.
![Multiple turns under power through tight fairways are required in marinas.](marina.jpg attrib="Van Isle Marina" attrib-url="https://vanislemarina.com/")
Navigating a marina and performing mooring operations under power on a sailboat is challenging. Because these tasks require moving at low speed and in areas with restricted maneuverability, more factors come into play.
The strength of the forces applying to a sailboat under power depend on the design of the boat. Some significant qualities are:
Single vs. dual rudders : Dual rudders lack prop wash under forward burst thrust.
Strength of prop walk : Shaft drives usually have more significant prop walk in reverse.
Keel shape : Boats with longer keel chord lengths are harder to turn and spin in place. Boats with deeper keels have fewer options in shallow water.
Windage : Multiple furled headsails, a stack pack main, and stern fixtures such as a bimini and solar panels increase the impact of wind on a boat in tight quarters and the efficiency of motoring long distances.
Navigation depends on motion of the boat relative to fixed objects. However, steering depends on the motion of the boat relative to the motion of the water. For example, a sailboat moving at 2 kts along with a 2 kt current has no ability to steer under power.
The momentum of the boat increases with its mass. It is harder to start and stop the motion of a heavier boat.
 
- - -The following diagrams show some of the elemental cases that arise under auxilliary propulsion. The next subsections discuss why they occur and how to leverage them to achieve effective maneuvers. With an understanding of these and remembering that the boat pivots around the keel, maneuvering in tight quarters can become mostly intuitive.
- Steering with forward prop thrust and forward way (relative to current): the boat pivots about its keel and steers away from the rudder. This is the "normal" case in forward gear.
- Steering with reverse prop thrust and aft way (relative to current): the boat pivots about its keel and steers towards the rudder. This is the "normal" case in reverse gear.
As with a car, steering backwards can be confusing. Step around to the other side of the wheel and face the stern, and then both the throttle and wheel act in the expected direction. Steering a boat in reverse this way can be even easier than in forward. There's unobstructed visibility and the helmsperson is closer to the edge of the boat to judge distances. The rest of the boat follows wherever the stern has passed through, like a snake.
- - -
-
Forward burst of prop thrust, with a single rudder, starting from zero boat speed: prop wash kicks out the stern, based on the rudder direction. On a shaft drive, there will also be a slight kick from the prop walk. For the common right-handed prop, this is to starboard when thrusting forward, so starboard bursts will be more effective than port ones.
-
Reverse burst of prop thrust with a shaft drive, starting from zero boat speed: prop walk kicks out the stern in a fixed direction independent of the rudder setting. For the common right-handed prop, this direction is to port when thrusting in reverse.
- - -
-
Current from ahead with forward thrust: the boat can hold position over ground and move laterally by steering.
-
Current from astern with reverse thrust: the boat can hold position over ground and move laterally by steering backwards, since the boat in reverse relative to the current.
-
Cross current: the boat skids sideways with the current.
- - -
-
Turning off the wind ("falling off" direction): the turn tightens because the bow is blown down.
-
Turning into the wind ("heading up" direction): the turn widens because the bow resists the turn.
-
Cross wind blows the whole boat laterally and also turns the boat by blowing the bow down until it reaches the quarter.
- - -
No steering via the rudder is possible in the following cases:
- Moving with the current: if the boat is moving at the same speed as the current over ground, then it is not moving relative to the water and there is no wash over the rudder, so it cannot steer.
- Forward burst with dual rudders while stopped: the wash passes between the rudders. There is no steering possible until the boat begins to move relative to the water.
- Reverse burst with a saildrive while stopped: there is minimal prop walk, so until the boat begins to move astern and generates wash over the rudder there is no steering.
The propeller is the main propulsive force under power until close enough to a dock to leverage lines ashore. Some boats also have bow and/or stern thrusters.
Excepting thrusters, boats require a wash of moving water passing over the rudder to steer. When the entire boat is moving relative to the water, this is maintained.
Independent of boat movement, a brief burst of thrust from revving the motor for a short time can create a local wash over the rudder. This localized moving water also deflects the rudder as a form of thruster.
Generally, one uses only enough power to have steerage and maintain way against the current and wind and no more when maneuvering within a marina. For example, keeping speed low enough to produce no wake and be able to stop quickly (less than 5 kts) when in main fairway and extremely slow (1-2 kts) when in a secondary fairway and actually docking.
The larger and heavier the boat, the longer it will take to respond to direction changes between forward and reverse. While waiting for the propeller to change the forward-aft movement, wind and current continue to act on the boat.
When in reverse, or forward in a boat with dual rudders, the rudder acts in the direction that the boat is actually going (its velocity), not the direction that the thrust (acceleration) is directed/the way you want to go. So, if the boat is moving forward and the helmsperson shifts into reverse, they must continue steering for the foward direction until the motion stops and boat actually starts moving in reverse.
However, on a boat with a single rudder, even immediately after shifting into forward there is prop wash over on the rudder. That can be directed by the rudder as a sort of stern thruster. This means that while drifting backwards, the helmsperson can shift into forward with a high throttle to suddenly force the stern to slide laterally as if they were moving forward, even though the boat is still moving backwards.
Older systems have separate gear shifts and throttle. Modern controls combine these into a single lever that automatically shifts into gear with the throttle. With a separate shifter, it is necessary to throttle down to low RPMs for a few seconds before shifting in or out of gear to avoid damaging the drive system. For a single single lever system, shift slowly down to neutral and hold it for a few seconds before changing direction.
Prop walk (asymmetric blade thrust) is the phenomenon where a single propeller causes a slight sideways force on the stern because the upstroke side of the propeller cycle is slightly more effective than the downstroke. The effect is significantly stronger in reverse, at high RPM, and with shaft drives.
The direction of prop walk depends on the orientation of the propeller. Most boats have right-handed propellers that walk to port in reverse and to starboard in forward. Depending on the vessel, prop walk can vary from effectively undetectible to so strong that a boat cannot turn in one direction to reverse.
Prop wash is the flow of water off the propeller. In forward gear with a single rudder, the wash flows over the rudder and provides some steering capability even at low speed. In reverse or on a dual rudder boat, the wash does not flow over the rudder, so steering requires boat motion relative to the water current.
Thrusters are electrically powered propellers or jets that can apply brief lateral thrust while docking. Single bow thrusters are most common on sailboats, usually those above 35' in length. Additional stern thrusters appear on even larger boats. A single thruster is useful for turning with a small radius. Two thrusters can allow turning in place as well as lateral movement without requiring a turn.
Fore and aft speed over ground stretches the radius when turning. Reduce speed by shifting into neutral or reversing direction to slow the boat and tighten the turning radius. Turning while moving upwind is also sharper than while moving downwind because the bow is blown by the wind in the desired direction and because the wind is helping to slow the boat and tighten the turn. Of course, one cannot go too slowly because some way is required to maintain steerage.
With care, it is possible to turn a boat within nearly its own length. This is necessary when turning around within a narrow fairway. To do this, the helmsperson must exploit momentum and change thrust directions while maintaining the turning motion, as well as leverage the wind. They pull to the leeward side of the fairway, shift into neutral, and turn the rudder hard to windward. As the boat turns, it will also get closer to the windward boats. The helm then reverses thrust briefly, while keeping the rudder over until the boat begins to move backwards. At that point the helmsperson throws the rudder the other way. The process then repeats when the boat gets closer to the leeward side, although more conservatively there, and continues alternating thrust and rudder orientation while always maintaining the turn's momentum in the same direction.
This is called a three point turn. In light wind it can be executed without ever making way in reverse (although the thrust must still be reversed to stop forward motion temporarily and tighten the turn). In heavy wind or a very narrow fairway, it may take many more than three points to turn.
If the boat has significant prop walk, ignore the wind and instead prefer to turn in the direction where prop walk assists the turn. This is turning to starboard (i.e., clockwise) for a boat with a common right-handed prop that walks to port in reverse. The turning maneuver is then called a back and fill and can be exceptionally tight. Note that prop walk fights the forward part of the turn and supports the reverse part. Usually the prop walk is more significant in reverse.
![Twin rudders on a Pogo 36](twinrudder.jpg width=350px attrib="SAIL Magazine" attrib-url="https://www.sailmagazine.com/cruising/boat-handling-docking-with-twin-rudders") Some recent performance cruisers pair twin rudders with a sail drive. This configuration is efficient for sailing and for motoring forwards long distances. However, it can be challenging to maneuver in tight quarters. Such a boat has no prop wash and minimal prop walk. Often the boat requires significant movement in reverse before there is any steerage available. It may require 5-10 seconds in reverse and cover 3 meters of distance before the boat can be steered.
In my limited personal experience with this configuration, I've found two strategies the best for maneuvering in reverse. The first is to initiate turns while moving forward, before changing direction. I use a brief reverse thrust without changing the helm to halt the forward velocity while maintaining the turn in place. If the rotation ends earlier than needed, I give forward thrust without touching the helm. This is like a back-and-fill, but does not gain the advantage of prop walk.
The second strategy is to turn the boat around long before reverse is needed, and back into the side fairway or dock from that long distance. This requires steering in reverse for longer, but ensures that the boat has steerage when the critical backing occurs because it was already in motion.
Current is rarely the dominant factor in tight maneuvers, and 1-2 kts of cross current or powering into current is easy to compensate for. There are three exceptions where it can get tricky, however.
One exception is navigating narrow or obstructed tidal channels, such as in the northern reaches of the Salish sea or tidal fjords.
Another exception is an estuary or river marina where current flows straight through, such as found in the UK.
In both of those cases, 5 kts or more might be experienced at maximum ebb or flood and become the dominant factor. Of course, one common strategy in each of those cases is to time one's maneuver close to slack water at high tide to avoid the current completely.
The third tricky situation with current can occur even within protected marinas. It is an example of elemental case #11 above. When the current is at docking speeds (1-3 kts) and pushing the boat into the slip or fairway, there is no steerage available because the water is moving with the boat over ground at the same speed. Two undesirable options are to move faster over ground than desired, or to periodically reverse thrust direction (case #6) and pull away from the destination in order to get wash relative to the current and reposition the boat.
When pulling in or out of a slip or narrow fairway with a significant crosswind, the impact of wind on the bow in particular must be taken into account. This often requires selecting the turn direction based on the wind and instead of the target path. That is, don't drive the boat as if it were a car.
Here are some examples of how the elements previously discussed can be combined to empower the skipper instead of fighting them.
In the
figure on the right, the boat begins in its slip at (a) and is docked
stern-to, off a narrow fairway. A strong cross wind is blowing in from the starboard
side of the boat. If the skipper attempts to turn to starboard as they
leave the slip, they will be turning into the wind. The cross wind
will blow the bow down and widen or prevent the turn before the skipper
can clear the opposite side.
A solution is to instead turn at (b) away from the main fairway, driving deeper into the narrow side fairway. The cross wind will help with this turn, making it very sharp.
Assuming port prop walk in reverse for this example, the skipper turns slightly past 90 degrees. They do this so that when they apply reverse thrust at (c), the prop walk straightens the boat in the side fairway. They then back out to the main fairway. If the boat had starboard prop walk then they would have turned more than 90 degrees, and if the prop walk was negligible then turning until directly aligned would be fine.
At (d), they initiate a relatively wide turn in reverse fighting against the wind. Again, the skipper intentionally over turns, ending pointed slightly towards the wind at (e), and getting close to the windward dock.
This positioning at (e) anticipates that the cross wind will blow the boat slightly, pushing it to port and turning the bow down while the skipper is waiting for the forward thrust to accelerate the boat out of the main fairway.
- - -Depending on the conditions and boat, two alternatives could be employed for leaving the slip in this scenario. In light wind, the skipper could perform a 180 degree back and fill turn at (c) to leave the narrow side fairway facing forwards and achieve a tight turn onto the main fairway with the wind helping. Or, in strong wind, they could back out of the marina the entire way, never fighting the cross breeze.
In the figure on the right, the boat enters the marina at (a)
with forward way and a cross wind from the port side.
When aligned with the fairway, the skipper turns through about 160 degrees in place at (b). There are two choices for that turn. With a strong prop walk to port in reverse, it would be easier to initiate the turn to starboard, clockwise. In the absence of strong prop walk, turning to port is easier because the initial portion of the turn has higher velocity, which is helpful for bringing the bow up into the wind.
The turn is slightly less than 180 degrees so that the bow is pointing a bit upwind at (c). Then, the skipper lets the boat blow down to its slip, and reverses into the slip at (d).
- - -
If the target slip were further down the fairway, a long drift sideways
could be hard to control. In that situation, the alternative shown
on the right could be used.
Here, the initial turn is separated into two parts. At (b) the boat only turns about 90 degrees, and then lets itself be blown backwards down the fairway, able to steer.
At (c), the skipper completes the turn. From the helm position, it looks as though they are turning too early and aiming to back into the slip upwind of theirs, or maybe the finger dock between slips. That is because while backing towards the slip, the boat will continue to be blown downwind and the bow will continue to turn. The skipper has to anticipate this by aiming for an upwind spot.
Note that prop walk is not a factor for this final turn. The boat has been underway in reverse down the length of the narrow fairway, so has full steerage and may not even be using reverse thrust.
- - -I would consider two alternatives for this scenario if the wind was very strong, to avoid the initial turn. The first is to simply dock bow-to, avoiding having to turn so far. For the first slip, no turn at all is needed in this case.
The second alternative is to back into the marina from the start, avoiding the initial turn if docking stern-to at the upwind slip, and avoiding ever coming to a stop with a three point turn when targeting the downwind slip. A large turn while stopped can be difficult in the presence of wind because there is no steering available at the stopped time but the wind will continue to act.
All aspects of sailing require multiple fallback plans and preparation to enact them immediately in the event of an emergency or other change of situation. A competent skipper is prepared to immediately take action while sailing if the boat broaches, an obstruction is sighted, or any equipment fails.
When docking or picking up a mooring, it is important to assume that one might miss the intended landing point or line cast and have a plan for how to abort the operation and try again.
It is also necessary to prepare to react to unexpected situations that are beyond the ability of the crew to prevent, as described below. While sailing, many external problems such as weather or obstructions can often be recognized some time in advance, and even equipment failures are frequently slow moving problems that give some time to consider and react. During docking and marina maneuvers, problems can arise with little warning or time to respond.
When operating under power, the skipper must constantly be prepared to escape an unexpected obstruction, an area where the wind or current have unanticipated strength.
The "unexpected obstruction" could be a rock, a submerged piling, or a closed off channel or fairway. It is most often a power boat, paddleboard, or kayak emerging from behind a dock or breakwater. Lacking masts, those small boats are hard to spot early and also likely have right of way.
If simply steering around the problem is insufficient, the remaining choices are stopping, backing away, and turning around. Consider which you'd use before the need arises and keep an eye on that "escape" route to ensure it is clear.
Always be prepared for engine or propeller failure, and have a plan for how to react. This includes having sails ready to raise any time you are moving under motor power.
Some likely causes of failure are running out of fuel (due to an incorrect gauge or the mistake of not checking), the prop being fouled, a loose propeller not rotating with the shaft, or an engine failure such as fuel or cooling system clog or broken pump.
Gaining control over the vessel takes priority over restarting the engine in this situation. Attempting to diagnose and repair the cause of the failure in time to recover control under power is usually not realistic.
When motoring in open water, there is generally a lot of time to respond to a propulsion failure. It is likely safe to drift for a bit while diagnosing the problem and planning the next move.
However, even in open water the motor may be needed in bad weather to maintain a safe heading relative to waves. In this case, there are several natural fallbacks. The first and best is of course to raise the sails and resume sailing.
If the conditions or rig preclude sailing for some reason, raising the sails in a reefed condition and heaving to is the next option. Towing warps or deploying a sea anchor or drogue are heavy weather alternatives to maintain steerage.
The time honored solution to propulsion failure in heavy weather is to raise sails and heave to, allowing you to wait out a storm or work on the engine and fuel system in relative safety.
In a mooring field or marina main fairway, you may be able to raise sail enough to gain steerage and reach clear water. Start with whichever sail is faster to raise. This is often the jib if it is already hanked on or is roller furling. Gaining some acceleration from a sail will retain flow over the rudder to allow steering.
Be sure to raise the main sail at the first opportunity, however, so that you can also change direction when needed. At low speed it is impossible to tack many boats using only a jib because it forces the bow down.
Of course, moving with full, trimmed sails within a marina would produce too much speed. Let the sails luff partly and keep them at the third reef point or smaller.
When against a leeward shore or in a tight spot in a marina, immediately dropping anchor may be the best way to stop boat motion. This can buy time to signal for help or repair the motor. It may be possible to lasso opposing pilings and cleats with dock lines to hold the boat in place in a fairway. The anchor is likely faster and more foolproof as a start. If the anchor is on a windlass, make sure that you know how to release it in the absence of power. This is usually done by releasing the brake with a winch handle.
In a well-protected marina or in open water under very calm conditions, the boat can be moved by towing from a dinghy, sculling with an oar or the rudder, or warping off pilings.
In the worst case, intentionally grounding at a safe location such as a sand bar may be preferable to being blown onto rocks or into other boats.
A less common failure mode for anchoring or mooring is when the sails cannot be dropped after the motor is engaged. Some causes of this are a halyard jamming at the masthead or inside of the mast, a headsail twisting around another forestay or instrument, an overridden halyard winch, a jammed halyard cleat, a sail being caught on a spreader, a furler overriding and jamming, the main jamming with a broken slide in the track, a battened main catching on a lazy jack, and a furling main overriding and jamming inside of the boom or mast.
Depending on the sea and wind conditions, being stuck with a sail up can vary from annoyance to serious danger. The amount of time to resolve it and choice of methods will be dictated by the sea conditions. A jammed furling headsail can be dropped using the halyard if it is possible to completely unfurl it. A halyard that is jammed at the bottom can be dropped by cutting the halyard (although--then you have a catastrophic problem when you need to raise the sail). Often a lightly jammed furling main or broken slide can be cleared by raising and redropping under appropriate tension.
In an extreme case, it may be necessary to cut a jammed sail free. This is not just expensive to repair later but also immediately dangerous, as the free parts fly about in the wind. It may also be necessary to send crew up the mast to free a jammed halyard or cut a sail free. That is dangerous in wind and waves, with a sail unfurled. The masthead will swing as the boat rolls, throwing the crew around and risking collision with the mast or stays, and the sails will luff into the crew.
There aren't really great options in some of these situations. Rely on careful inspection, preventative maintenance, and raising and lowering sails correctly to avoid them happening in the first place. Then, improvise when needed.
What are the actual chances of needing to execute on a fallback plan under power or docking? Having to back out of a fairway or dodge an unexpected vessel is a fairly common occurence in my experience. Motoring in a marina is like driving a car in busy parking lot, where you know that others will be backing out and pedestrians will be dashing between cars all of the time. In this analogy, paddleboarders and kayakers are the dashing "pedestrians" of a marina.
A lightly jammed headsail that can be freed by pulling it back out and refurling is also fairly common, especially on a charter boat where you don't maintain the furler and may not be familiar with its idiosyncrasies.
How often a furling main jams seems to depend highly on the furling system and the skipper. Sailor bars and online sailing forums are full of debate on this point. Claims vary from considering mainsail furling to be a death trap to insisting that the main can reliably be furled in a storm.
A tragically timed engine stall is something that doesn't shock me on an older boat or a smaller one with an outboard, but isn't an everyday problem. If it is an everyday problem, then you need engine maintenance! (Or, forget the thing exists and always plan to dock without it.) A well-maintained inboard engine that has just been inspected, has clean fuel, and is navigating through sufficiently clean water is not the most likely failure point when motoring through a marina. Maybe one in fifty times there will be an unwelcome surprise here.
A jammed or loose propeller can produce a situation that isn't possible to correct in the moment. Jamming in a marina largely can be prevented by keeping a close eye on lines and stopping the prop if one comes too close. However, monofilament fishing lines are effectively invisible and some people have an annoying tendency to fish right in channels. Outside of a marina, trash, lobster and crab pots, and free-floating discarded fishing lines can be a source of lines in the water that can tangle the prop. Even in the open ocean there are unfortunately cast loose fishing lines and net and trash. A loose propeller can be avoided with frequent inspections on one's own boat, but is a hazard on a charter.
I've occasionally experienced halyards jamming with the sails raised on small rental/charter keelboats, after sailing in strong wind. This happened from either from the sheave breaking at the top or the halyard jamming in the cleat at the bottom. I think those could have been prevented by better inspection and maintenance, as well as sizing the cleats, blocks, and halyards appropriately.
I've fortunately never had a halyard jam on boats that I maintained, but I've learned to carry a rigging knife when on someone else's keelboat. I'd rather apologize and pay for cutting their halyard than for sinking their boat in a storm.
With proper care in well-known waters, serious grounding is extremely rare. However, even with careful attention to charts and tide tables, with enough sailing time it a question of when, and not if a grounding will happen--and whether it is a slightly embarrassing pause on a sandbar, or a life threatening catastrophe with waves pounding the hull into a rocky shore.
I don't know anyone with significant sailing experience who hasn't grounded at some point. How often grounding occurs depends on where and how you sail. My own experiences have been largely with silted-in channels at low tide and isolated submerged rocks in unfamiliar waters.
An apparently light grounding that one escapes can still cause a serious propulsion problem if the propeller or shaft is damaged in the process. They are protected by the keel in a head-on collision with an underwater obstruction. However, they can be damaged if the boat twists while it is grounded on rocks or a reef.
Most 30' and larger keelboats have an internal diesel engine or diesel generator for either directly driving, or powering via batteries, the auxilliary propulsion mechanism.
A diesel engine requires a functioning electrical system and power to start or stop, but not to continue operating. So, one turns on the engine's electrical system first, then starts the engine, and then leaves the power on until after the engine is later stopped. In an emergency, a diesel engine can also be stopped by manually depriving it of fuel. A diesel engine will not start if it is below about 8 degrees C, so electric glow plugs can be used to heat it for a few seconds when the ambient temperature is cold.
Marine diesel engines use seawater for cooling and will be damaged and stopped if the cooling system fails. When turning on a marine diesel engine, immediately listen for the cooling water emerging from the boat. If it is not, stop the engine and check the filters, stopcocks, hoses, and water pump/impeller. The exhaust gas is mixed with the expelled water, so there are relatively few fumes.
On boats without separate batteries for them, the other mooring electrical systems may require the engine operating to have power. For example, it is common for a bow thruster and anchor windlass to only operate when the engine is running.
Unlike other fuels, diesel is not explosive at normal temperature and pressure. For example, a match dropped into a bucket of diesel will be extinuished instead of lighting.
![ ](fueldock.jpg width=350px attrib="Departure Bay" attrib-url="https://departure-bay-gas-n-go.business.site/") Marine diesel (MDO) is naturally colored light yellow (which is called "white") and can be hard to distinguish from dirty water. It is visually indistinguishable from automobile diesel when undyed. MDO may contain more heavy fuel oil and less bio-diesel than automobile diesel. That is advantageous. It may have a higher sulphur content, which is disadvantageous. However, both fuel products are intended to power the same engines.
In some regions, marine diesel dyed red to distinguish it for tax purposes. The red dye incidentally helps make spills and leaks more visible. In the US and Canada, all marine and off-road vehicle diesel is red and untaxed, unlike on-road automobile "white" diesel. In the EU, lower-taxed red diesel is reserved for commercial vehicles. In UK (2023, post Brexit), lower-taxed red diesel may be used by recreational boaters. Recreational boat captains may need to have documentation on where the fuel was purchased when entering a different region if using red diesel, to show that it was taxed correctly where purchased.
Diesel will float on top of both fresh and salt water. This includes in the fuel tank--water contamination and condensation will sink to the bottom of the tank and must be pumped or siphoned from the bottom instead of the top to remove it. Small amounts of water contamination also accumulate in the bottom of the primary fuel filter and can be drained there.
![Diesel bug](dieselbug.jpg width=350px attrib="Yachting Monthly" attrib-url="https://www.yachtingmonthly.com/sailing-skills/how-to-avoid-diesel-bug-32632") Diesel bug is contamination by bacteria and algae within the fuel tank. It is exacerbated by the use of bio-diesel (which is pervasive today to reduce fossil fuel production) and water in the tank. It can be mitigated by keeping the tank clean and nearly full, reducing the volume available for oxygen and water vapor. Contaminated fuel can be cleaned by filtering.
Marine and heavy equipment diesel engine service is measured in engine hours, not distance as in an automobile. Because the engine is usually run at a fixed speed that is most optimal, fuel consumption is correspondingly measured in litres (or gallons) per hour. For example, the Volvo Penta D2-55 (Perkins 404) engine consumes about 2L/hour in real world usage combining idling and revving up to 2500 RPM.
The diesel fuel may also be used for a diesel heater. Modern heaters are extremely efficient. For example, a Webasto heater consumes about 0.3 L/hour.
![Standard Yanmar engine start/stop/RPM panel](yanmarpanel.jpg width=350px attrib-url="https://www.yanmar.com/marine/product/panels/b20/") In preparation, check the following before sailing:
- Fuel level in the tank
- Belt tension
- Oil level and clarity with the dipstick
- Pan under the engine for oil leaks
- Water and fuel filters
- Water intake stopcock (should be open)
Record the engine hours and fuel level in the log.
When starting the engine:
- If at night, turn on the steaming light
- Check the water for lines, animals, and swimmers
- Put the drive in neutral gear and the throttle at idle. This is just the center/neutral position in a single-control system.
- Turn on the electrical power to the engine. There should be a continuous alarm when it is on
- If it is very cold, hold the glow plug button for a few seconds. The amount of time depends on the engine and the temperature. Check for clear water again right before starting.
- Press the engine start button
- Verify that the cooling system is operating. You should hear water splashing from the exhaust port immediately in bursts. In a marina, you can usually see it over the side as well. Shut off the engine if water is not being expelled.
Leave the electrical power on while the engine is on. The power is needed to shut it off again.
- Ensure that you are firmly moored or have sufficient way under sail for steering
- Lower the throttle to idle speed and put the engine in neutral
- Press the engine stop button
- Turn off the electrical power to the engine
- If sailing at night, turn off the navigation steaming light
- Put the drive in gear
The propeller will turn the shaft when the boat is sailing if the drive is left in neutral. This can cause wear and damage the engine. To prevent this, most systems require that the drive be left in gear when the engine is off. This could be either forward or reverse gear depending on
The traditional drive system for a boat is a propeller shaft directly in line with the engine and run out through the hull to a propeller. The stuffing box minimizes the water ingress where the shaft penetrates the hull, but will weep small amounts of water in normal operation.
![Shaft drive](shaft-drive.jpg width=350px attrib="BoatsNews.com" attrib-url="https://www.boatsnews.com/story/25131/shaft-line-for-sailboats-the-queen-of-propulsions") The design of a shaft drive is typically constrained such that the shaft is at a slight downward angle as it exits the hull. This means that the propeller is not pointing straight backwards but instead slightly downwards as well. This angle gives rise to prop walk, where varying force exerted by the blades on the bottom and top creates a lateral force on the stern of the boat. Prop walk is advantageous for accelerating turns when in a marina, but reduces the efficiency of motoring straight for long distances.
 A saildrive is like the shaft and propeller of an outboard engine, but mounted to the inboard engine. It connects to the back of the engine and projects downward from the bottom of the hull.
Saildrives have several advantages over shaft drives, which has led to their nearly universal application in new boats. Only a handful of manufacturers use shaft drives today (such as Rustler and Island Packet).
Saildrives create less vibration and noise underway. They are more efficient than shaft drives when traveling straight for long distances. They consume less internal volume, creating more room for storage and accomodation. The seals do not weep and are less likely to leak than a stuffing box, keeping the bilge drier.
There are also drawbacks of saildrives compared to shaft drives. They require professional maintenance every 5-10 years. The enclosure is made from aluminum, and requires sacrificial anodes and frequent monitoring to avoid corrosion.
![Saildrive projecting from hull](saildrive-exterior.jpg width=300px attrib="Yachting Monthly" attrib-url="https://www.yachtingmonthly.com/gear/essential-saildrive-checks-for-your-boat-77913") The relatively minimal prop walk in reverse makes turning more difficult by precluding the back-and-fill maneuver, perhaps requiring a bow thruster to compensate on longer boats. The through-hull hole for a saildrive is very large compared to a propellor shaft hole. It is sealed by a major gasket and has a separate leak alarm.
Electric saildrives, such as Oceanvolt Sail Drive, are not mechanically coupled to the engine. They instead use electric motors to power a saildrive.
This fully unconstrains the location of the generator, or allows removing the generator entirely if an alternative source of power such as solar and large batteries is available. While sailing, the propeller can also be used for regeneration, creating a small amount of drag and recharging the batteries.
Electric saildrives are nearly silent and allow operation with the generator off. They provide power instantly and do not require the careful spin up time of a mechanical drive to reach high amounts of thrust. They also allow the generator to be run at its most efficient RPMs independent of the speed of the propeller.
![Systems devoted to propulsion for an Oceanvolt SD installation](oceanvolt.jpg attrib="Oceanvolt" attrib-url="https://oceanvolt.com/solutions/systems/sail-drive/")
The primary downside of electric saildrives is that they are a bit ahead of their time for most sailors. Their power requirements in turn lead to the necessity of LiFePO4 batteries, which creates a complex and relatively new system compared to the less expensive, proven, and easy to repair/source parts for diesel engine and AGM batteries.
On monohulls, it is difficult to achieve sufficient power for recharging without using diesel. A large catamaran has enough coachroof and deck area to use solar. This means that monohulls with electric saildrives are still using diesel generators (reducing many of the electric advantages), required to recharge by shore power frequently, or dominated by power conservation concerns when operated.
Two cruising YouTubers who use electric drives on monohulls are Sailing Uma and Sailing Oka Solo. They demonstrate that it is possible to go fully electric if one is willing to have power conservation be a dominant factor in daily planning.
When comparing diesel and electric engines, 746 W = 1 hp (imperial horsepower; metric horsepower is slightly less) of propulsive power in terms of mathematical unit equivalence. Beware that the power draw of the motor is different than the resulting propulsive power. The propulsive power in watts is what you should compare with. However, there's more than raw units at work in the comparison. In practice, the effective comparison is closer to 330 W = 1 hp at low/displacement speeds.
A propeller's efficiency depends on the number of blades, their size, and their angle of attack. Sailboat propellers usually fold when not in use to reduce drag, which tends to restrict them to two or three blades. Even rigid props typically have three blades to reduce their drag under sail.
Propellers must be protected from galvanic corrosion by sacrificial anodes. For salt water, these are made from zinc and so are often called "zincs".
Propellers are vulnerable to catching loose lines in the water. High risks are a boat's own docking lines and sheets, fishing lines, and nets. Snagging a line can immediately disable a propeller. The helmsperson should constantly check for loose lines and be paranoid about lines falling in the water. A linecutter attachment on the end of the shaft is a circular set of blades that can sometimes protect the propellor by shredding lines that are encountered moving from bow to stern.
A recent research design for propellers eliminates the tip vortex drag by using a toroidal shape that has no tips on the blades. Unfortunately, this is not practical for a sailboat folding prop.
A bow thruster provides lateral force at the bow. It is typically a propeller with an electric motor mounted in a tunnel at the bow. This can be used for turning the boat while docking. Most modern boats over 40' use bow thrusters because their heavy mass makes them hard to turn tightly.
 A bow thruster can also drop down from a compartment in the bow. This reduces drag under sail. The drawback is that it is more likely to catch lines and seaweed, is a part that can fail, and there is more delay to engaging the thruster.
Less common on sailboats are stern thrusters, which typically drop down in the stern. Using both bow and stern thrusters enables translational movement away from a dock on very large boats and can enhance the ability to spin in place.
Jet thrusters are like a jetski, and pump sea water through at high speed to create thrust. The drawback of these is that they pump seawater at high speed through the boat, which is a high risk if a hose breaks loose. A typical bow thruster has only a very small through-hull connection for the electrical wires and is otherwise completely sealed outside the boat, eliminating the risk of leaks.
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