How to Adjust an Outboard Motor Angle for Best Performanceby Erick Kristian
Outboard motors are engines mounted on the outside of the stern of the hull. All outboard motors have an adjustable trim angle. The trim angle is the angle of the motor in the water. The optimum trim angle varies by motor, boat, conditions and speed. There are three main trim angles. Neutral trim occurs when the motor is parallel to the stern. Trimmed in occurs when the motor is as close to the stern as possible. Trimmed out occurs when the motor is farthest from the boat.
Put the outboard in the "Trimmed In" position. This is the best position to start off with. Some outboards may specify ideal angles in the owner's manual. This can be done on manual outboards by loosening the trim lever and pushing the top of the engine out away from the boat. The result is the propeller moving closer to the boat. Tighten the trim lever when done. On a power outboard adjust the trim lever to the farthest in position; the trim lever controls the angle of the motor. Trim in the motor on crafts that have a heavy bow to help reduce drag.
Start the motor and monitor the performance of the boat. Lock the throttle in at a reasonable cruising speed. The best trim angle should have the boat riding level and the majority of the hull on the surface.
Adjust the motor from the "Trimmed In" position outward and see what happens to the performance of the boat. Does the boat go faster? Monitor the performance as the trim is pushed outward. Note the RPM and speed relative to the different angles. There is no one ideal angle -- it always varies by boat. Put the motor into a neutral trim, where the propeller is parallel to the back of the boat. In an evenly weighted craft this should be a fairly fast position and in a craft with only the driver, it will likely be the fastest.
Stop adjusting at the "Trimmed Out" position when "Ventilation" occurs. Ventilation occurs when the propeller blades are not always fully submerged. The ideal position for most boats occurs just before ventilation or when the increase in trim results in higher RPM and not increased speed. Trim out only when the craft is stern-heavy.
- "Outboard Engines: Maintenance, Troubleshooting, and Repair, Second Edition"; Edwin R. Sherman; 2008
- "Outboard Motors Maintenance And Repair Manual;" Jean-Luc Pallas; 2006
- "Understanding the Outboard Motor"; Eugene Stagner; 2002
- "Skipper's Outboard Motor Guide"; Hans Donat; 2011
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