Optimax 150 tilt motor came on while while cruising

[Sidenberg]

Year 2000 Optimax 150. The Outboard was all the way in the down position already when the tilt motor turned on to the down position, thank goodness. I cut the outboard but the tilt motor kept running. I first thought it was the bilge pump as the sound seemed to be coming from the bilge. The only way to shut it off was to switch the batteries off but when I switched the batteries back on the tilt motor started running again. The tilt motor turned off after about 10 minutes on its own but then started up again for no reason. I would appreciate any ideas where to start looking for the problem. Relay switch? ad on off switch?

[boats.net]

Probably have bad trim switch, probably water in switch.