Many boaters have trim tabs and rarely use them. Others may use some tab if an overweight passenger leans the boat to one side. But so many benefits can be derived from trim tabs that they should be a constant for any operator.
From The Start
A planing hull usually experiences the bow rising when you initially advance the throttle. That causes the thrust from the prop(s) to be aimed farther downward, robbing you of efficiency. It’s not until the boat builds enough speed to pass its own bow wake that the bow drops and the boat can proceed at a less dramatic running angle. This process uses extra fuel, sometimes can obscure the helmsman’s vision forward and lengthens the time it takes to get on plane. This poses a particularly annoying problem to boats with high-performance propellers designed to perform optimally at high speeds but have little low-end torque (poor hole shot).
To avoid these issues, make sure that your engine is trimmed all the way down and that your trim tabs are extended to the max, then throttle up. The boat remains much flatter, cuts through the bow wake rather than riding up and over it, and channels the thrust more parallel to the water’s surface for peak efficiency. You’ll find that this method can cut seconds off time to plane. However, once on plane, the tabs should immediately be retracted to normal running position as should the engine tilt. Otherwise, you could find yourself suffering from bow steer — a very awkward sensation and potentially dangerous.
Up Sea/Down Sea
Most planing hulls run at an angle such that the oncoming water meets the hull about one-third of the way back from the bow.
The hull form is sharpest right at the bow and then as the deadrise lessens, gets flatter as you move aft. Just as your hand moving flat through the water encounters more resistance than when it slices through sideways like a knife, so too does the hull. The sharp bow can slice through the water more readily than the flatter bottom farther aft. So if you find yourself running into a head sea, extending your trim tabs to drop the bow some will make for a smoother ride. Again, be careful not to trim down too far or steering will suffer and you’ll generate much more spray. Don’t have trim tabs? You can accomplish much the same effect by trimming your engine down to lower the bow, too.
Conversely, when running down sea, you would rather your bow carry up and over waves rather than carving through them. The latter causes lagging and makes the bow tend to swerve. Instead, raise the tabs fully and trim the engine up to normal cruising angle and run through the waves at a prudent speed to stay straight and dry.
Under most circumstances, you want your boat to run as close to level in all directions as possible. As mentioned above, if you have too much gear or people weight on one side, you can deploy the trim tab just on that side until the boat runs upright again. But that’s not the only time for lateral adjustment.
When running in a beam sea and wind, the waves meet the vertical freeboard of your hull and then take the path of least resistance — straight up. That causes that annoying spray to blast across your decks, often soaking everyone aboard. It also makes an uncomfortable slam each time a wave strikes.
While it seems odd at first and for those who don’t understand the process, lowering the trim tab on the upwind side of the hull, causing the boat to lean downwind works miracles. When the waves hit you broadside now, the chine is higher and the wave gets wedged underneath it. This causes the spray to travel downward instead of up. It also helps prevent those slamming jolts.
The market offers several types of trim tabs: recessed and not, electric, and hydraulic. Some companies even offer automatic tabs that you can set once so that they deploy fully when you start and then automatically retract to cruise mode according to your speed.
No matter what kind of system you have, you should always remember to neutralize them when you start fishing. More than once a captain with his tabs down has backed down hard on a fish and broken the tabs off from the water pressure. The ideal system has an actuator that automatically retracts the tabs whenever you shift your gears to neutral — something you naturally do when maneuvering on a fish.
Making best use of your trim tabs will save you money, make boating more pleasurable for you and your guests, and save wear and tear on your boat.