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Catamaran maneuvering under power

2017 October 1

Coaxing a big cat into a tight space requires a new way of thinking and a bit of practice

Catamarans are by far the favored boat for charterers, and charter fleets, which are full of cruising catamarans with a handful of monohulls reflect that. And it’s easy to see why: Not only is there room for a crowd to be comfortable, but the shallow drafts of catamarans allow sailors to nudge up close to the beach and enjoy a stable platform.  But being at the helm of a big cruising cat can be intimidating for a skipper used to handling monohulls, and we’re not talking about the sailing part. Much of the time, and certainly any time you’re in close quarters, you’re going to be operating that cat under power.


But there’s good news: If you’ve ever steered a shopping cart, you’ve already got a feel for how to drive a cruising cat under power.

It’s the beauty of twin engines, something sailors rarely get the opportunity to enjoy. In fact you’ll find that strictly speaking, you have a lot more control with the twin engines on a big cat than the single engine on a monohull. And with the extra windage on a tall cat, that control is going to come in handy.

Before you fire up those twin engines though, keep in mind a few important differences between operating a sailboat with two engines vs. a single engine. Most cruising cats have very shallow keels if any, so directional stability will come from the long, thin hulls as opposed to a keel on a monohull. In either case, water flow over the hull is needed to keep the catamaran going in a straight line. The more speed you have the better directional stability you will have. This is not to say that you should approach every docking situation at full speed, it’s just that in some situations a little boat speed can be your friend.

The key thing to remember about maneuvering a catamaran under power is that in close quarters or when docking, you won’t be steering at all. In fact, you can do what no driving instructor ever would have advised, and take both hands off the wheel. Everything happens on the gearshifts at this point. Differential power offers tight control. Need to turn to starboard? Nudge the left (port engine) gearshift forward and the right gearshift (starboard engine) back. If you need to spin tighter, give each controller a bit more throttle in the appropriate direction.  Think of it like steering a shopping cart—push with one hand and pull with the other. Small adjustments in course can be done by leaving one gearshift in neutral and pushing a little throttle on the other one.

Once you have water flowing over the rudders at about 2 knots of boatspeed, you can go back to using the rudders to steer the boat. Simply level the throttles to the speed you need and steer with the wheel as you normally would. If you’re battling current or cross waves, you may have to nudge one throttle up a bit to counteract leeway.

Maneuvering a boat with twin engines is a different experience for monohull sailors, so it’s a good idea to practice a bit in an open area where you can’t do any damage. Play with the gearshifts and get a feel for how tightly the boat turns depending on how much forward and reverse power you give the engines. Line up near a buoy or marker so you have a point of reference and practice maneuvering around it, even lining up with it as though it were a dock. Any amount of practice will help a skipper get a feel for just how many rpm will be needed in close quarters.

Most charterers will find themselves picking up a mooring ball and a catamaran’s twin engines make this an easy task. The key is to approach the mooring downwind or downcurrent, which allows better control as the props are closer to the force that is likely to cause slippage or leeway. But current and wind are rarely perfectly aligned and this is where a little preparation and practice comes into play. When you’re picking up a mooring you have the luxury of pausing for a minute before you approach it to get a feel for which way the boat is pushed by the wind or current. Once you know that, you can adjust your angle of approach to account for that, often between downwind and downcurrent. From there, it’s just a matter of using the gearshifts and differential power to steer to the mooring ball.

You will rarely be afforded the opportunity to scope out the situation before docking, however. If you have an option of docking bow first or stern first, again, aim to keep the transom upwind and upcurrent. If the two don’t align, unless it is extremely windy, it’s usually better to account for the current and keep your transom pointed into it. Docking a cat isn’t much different from a monohull, but the twin engines allow for greater maneuverability. If the boat is being blown off the dock, a bow line or stern line can quickly be made fast and used as leverage to crab closer to the dock. The same can be done with spring lines to hold off a dock. 

There is one important difference between monohulls and some catamarans that is important to note. On some cats, the props are aft of the rudders, and when you put the engines in a hard reverse, the propwash will spin the rudders hard, something you obviously want to avoid. It’s also important to remember that the propellers on cats are much farther outboard than on a monohull, so you have to be more careful about not fouling the props with dock lines and dinghy painters.

Of course there is one other great advantage in addition to maneuverability afforded by twin engines. If something does happen to one engine, you can still rely on the other. In fact, if you want to conserve some fuel on long passages, you can use just one engine and offset the angle by steering into that engine a bit. Just be sure to use the other engine the next time so the hours between both remain consistent over time.

Beyond the maneuvering differences, operating a catamaran under power isn’t different from operating a monohull. At cruising speed, the engines should still be at about 80% of maximum power (if you’re chartering, make sure to ask what the cruising rpm should be) in both engines. Start and shut off one engine at a time. From there it’s just a bit of a getting used to the shopping cart approach to maneuvering.