I have a 1996 75 HP Mariner on a bass boat. While in Texas last week it worked great for 3 days then it went SNAFU. If stopped dead in the water, it would raise and lower the motor perfectly but if moving any at all it would not raise the motor to trim out the boat. If you raised the motor before moving it would pull the motor back down. We pulled the boat out and checked the fluid level then drained. Got maybe a tablespoon out of it thru the plug hole. Added more fluid the tried again. Still the same results. Then we pulled the boat out and onto the trailer again, checked the plug on the side and it was tight. Loosened it then retightened. Put the boat back in the water again and took off. Worked good as new. That afternoon we went out to fish again and it was back to the same problem. It wouldn't raise the motor while underway. Any suggestions?