Yamaha 90D Owner's Manual

Contents

Operation32ciency. This is generally when the keel line ofthe boat is up about 3 to 5 degrees. With thebow up, the boat may have a greater tenden-cy to steer to one side or the other. Compen-sate for this as you steer. The trim tab canalso be adjusted to help offset this effect.When the bow of the boat is down, it is easierto accelerate from a standing start ontoplane.Bow UpToo much trim-out puts the bow of the boattoo high in the water. Performance and econ-omy are decreased because the hull of theboat is pushing the water and there is moreair drag. Excessive trim-out can also causethe propeller to ventilate, which reduces per-formance further, and the boat may “por-poise” (hop in the water), which could throwthe operator and passengers overboard.Bow DownToo much trim-in causes the boat to “plow”through the water, decreasing fuel economyand making it hard to increase speed. Oper-ating with excessive trim-in at higher speedsalso makes the boat unstable. Resistance atthe bow is greatly increased, heightening thedanger of “bow steering” and making opera-tion difficult and dangerous.NOTE:Depending on the type of boat, the outboardmotor trim angle may have little effect on thetrim of the boat when operating.EMU27931Tilting up and downIf the engine will be stopped for some time orif the boat is moored in shallows, the out-board motor should be tilted up to protect thepropeller and casing from damage by colli-sion with obstructions, and also to reducesalt corrosion.WARNINGEWM00220Be sure all people are clear of the out-board motor when tilting up and down,also be careful not to pinch any bodyparts between the drive unit and enginebracket.WARNINGEWM00250Leaking fuel is a fire hazard. If there is afuel joint on the outboard motor, discon-