The alignment of your outboard motor plays a crucial function in how well the boat performs through all speed ranges. An engine aligned off-center, too high or too low can have a negative effect on speed and turning response. Improperly aligned motors can also result in excessive engine wear and failure and increased fuel consumption. Several adjustments of the motor position determine how well it delivers maximum torque and response. Test drive your boat to determine how well it handles, then adjust the motor to bring it within maximum performance tolerances.
Trailer the boat and park it on a hard, level surface. Place a bubble balance level on the transom. Use a floor jack to lift the trailer frame in order to level the transom. To check your motor bracket position against the transom center line on your boat, use a tape measure to record the distance from one transom end to the other. Write the number down. Divide the number in half and mark that position with a felt pen on the top of the transom rail.
Tape a string with a weight on the end of it and hang it from the mark. The width of your transom bracket should be equally divided on both halves of the string. Adjust your motor bracket clamps to center your engine. Swivel your engine perpendicular to the transom surface to see if the prop shaft aligns with the bottom of the weighted string. If the prop shaft does not align, adjust your motor bracket accordingly.
Turn the engine, using the tiller handle or the steering wheel, through it full rotation left and right. There should be equal clearance on both sides when the engine reaches full stop on both sides of the transom or jack plate. Adjust the jack plate or shim one of the engine clamps to bring it within alignment. Check to see that the cavitation plate sits horizontally with the lowest part of the hull. Adjust the bracket clamps or jack plate bolts to correct it.
Launch the boat in water and start the motor. Let the motor idle while you inspect the lower drive unit and propeller. The water exhaust port of the lower unit should be sitting at least one inch above the water line to prevent restriction and overheating. The lower unit depth should allow the water intake ports to be submerged at least three inches under water.
Take the boat out and open the throttle up gradually. Look at the profile of the bow and whether it points up or down. Some upward lift will be normal, until the boat reaches planing speed; then the bow will dip down and the boat will increase in speed dramatically. If the boat continues to ride in a bow up position and fails to reach plane, adjust your trim either electrically or manually.
Bring the bottom part of the motor inward toward the transom to reduce excessive bow profile. To adjust electronically, activate the dashboard control switch for trim "in" positioning. For manually adjusted motors, remove the motor bracket bolt with the quick release pin, tilt the engine so the lower unit moves closer to the transom position and replace the pin. For the manual adjustment, try one adjustment hole at a time.
Notice if the bow points down and stays down while increasing the throttle to maximum speed. If the bow “plows” in this fashion and fails to allow the hull to plane, it means the trim has been set too far in. Adjust an electric trim using the dashboard control switch to set the trim further out, away from the engine. For a manual adjustment motor, pull the quick release pin on the motor bracket and set motor further out one notch, away from the transom.
