I recently picked up a 1988 Larson Citation DC-150 that has a Force 50 (by US Marine) of the same vintage. The motor has no trim control. When I put the motor in reverse and give it some throttle, the motor rocks up and the prop comes out of the water. I looked for some kind of manual lockout device on the motor to prevent this, but I can't find anything. I'm sure this is an elementary question with an elementary answer, but I am baffled at the moment. I've never owned a boat with an outboard before and am a bit lost here.