TRIM & TILT
Used properly, you’ll find power trim and tilt is a very effective and essential tool for comfortable boat-handling
Essential engine advice.
BEING ABLE TO CORRECTLY trim an outboard engine is an essential skill for anyone who drives a boat. A powered craft with its engine trimmed in the right manner is faster, more fuel efficient, comfortable for the crew and, most importantly, safer at high speed. Properly trimmed, the hull moves through the water with a slight bow-up attitude. With insufficient trim the bow continually tries to force its way through a bulge of water rather than skimming smoothly across the surface. Too much trim and the engine forces the boat out of the water, causing the bow to slam because its weight continually battles with the thrust of the engine.
STARTING OFF
Assuming the sea is flat calm and the ground you will be covering is deep enough not to pose a hazard, and, of course, having attached the kill cord, here is the procedure to correctly trim a fast-planing hull for optimum performance under ideal conditions:
1 Start with engine trimmed down fully and slowly push throttle forward to its maximum.
2 Wait a few moments until the boat is going as fast as possible, then slowly start to trim up the engine. Engine revs will rise, and the bow will lift slowly. e boat’s speed will increase.
3 Gradually increase the trim by raising the engine leg until the bow starts to porpoise through the water. At this point you have overtrimmed the engine.
4 Slowly trim the engine leg down to the point where the slamming stops. Now the boat will be running at the optimum trim angle for maximum speed in the conditions. Reduce the revs to cruising speed and the boat will continue to plane providing a comfortable, fuel-efficient ride. As you become familiar with a boat and its engine, you will be able to establish optimum trim without going through this process.
ROUGH CONDITIONS
If the wind picks up, the sea state deteriorates or you run into rough conditions in the vicinity of a tide race, maintaining the same speed will result in the boat starting to slam.
Aside from being uncomfortable, this runs a significant risk of damaging your GRP boat.
e ideal trim angle will be with the boat running with her bow slightly raised. Even with significantly reduced revs it is likely, when heading directly into the waves, that the bow will slam if you have the same amount of trim you had previously under calmer conditions. You will probably need a slightly lower angle of trim to maintain a comfortable ride.
If your course results in the waves and swell running directly astern, you will find that trimming out the engine and slightly increasing the angle of trim of the bow will provide the optimum cruising angle. is is because the bow will be raised slightly higher with less risk of forcing itself into the sea as the hull rides off each wave or swell. Stuffing the bow into a swell is uncomfortable, may create excessive amounts of spray, and can be hazardous because it can stop the boat and throw everyone forward.
TIGHT TURNING
Another occasion when it is necessary to adjust the trim while underway is when you want to perform a very tight, high-speed turn. If running at speed with the engine trimmed out, were you to suddenly throw the boat into a tight turn it is likely one of two things will happen.
Firstly, the propeller will cavitate (lose its grip in the water due to not being adequately submerged), resulting in it spinning in aerated water caused by the turbulence. You will have to stop and allow it to settle for a moment, before you can continue. e second and potentially more hazardous scenario is that as you run into the tightest part of the turn the propeller loses its grip in the water, resulting in the boat sliding off to one side.
In order to perform a tight high-speed turn, first start reducing the angle of trim, thus lowering the engine leg and propeller deeper into the water. At the same time, ease back the throttle but not so much that the boat comes off the plane. As the boat completes the turn, very slowly increase the revs to the desired speed, while at the same time increasing the angle of trim back to its original position.
RUDDER STEERING
In addition to being a source of propulsion, an outboard engine serves as a rudder providing steerage. e rudder effect is at its most efficient when the engine leg is trimmed down fully and progressively less so as it is trimmed up. When you perform a slow speed, closequarters manoeuvre, such as when moving in or out of a berth in a marina, you gain more control with the engine trimmed down fully, providing you have sufficient depth of water.
Loss of steerage can occur when returning to a launch site, which invariably means entering shallow water. In order to prevent damage to the propeller you have to progressively increase the engine trim as you enter shallow water. It means that at the precise time you need the most control of your boat you are compromising your ability to steer it. ere is no real solution here, other than to follow the golden rule of boat handling: proceed slowly while continually assessing, especially if you are unfamiliar with an area. Slowly creep your way into shallow water while gradually easing up the engine trim. You will get to a point where not only will the engine be trimmed up so much that you will you not be able to steer the boat effectively, but also the intakes for the cooling water will be raised out of the water.