I have a 1998 fisher ski bass boat with 200 mercury FX. when on the lake while running motor, on once in awhile the outboard motor tilt trim will rise up, and I will shut motor off but the trim will stay running keeping the tilt trim motor against the top back of boat, and the only way to shut it off is to disconnect the battery cable off. But is hard to get to when the motor is on top of the panel to get to the battery. what could it be that the motor goes up while running the boat on the lake? even the throttle tilt trim will not move the trim down or up.