Yamaha F2.5A Owner's Manual

Also see for F25A: Service manual Owner's manual Service manual Service manual Owner's manual

Contents

Operation53EMU27913Adjusting boat trimWhen the boat is on plane, a bow-up attituderesults in less drag, greater stability and effi-ciency. 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. When the bow ofthe boat is down, it is easier to acceleratefrom a standing start onto plane.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.TIP:Depending on the type of boat, the outboardmotor trim angle may have little effect on thetrim of the boat when operating.EMU27924Tilting 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 lower casing from damage bycollision with obstructions, and also to re-duce salt corrosion.