I've a Mercury Mariner 90hp, 2006.
Out of the blue the PTT is operating on its own!
After the boat has been sitting a while - 20 mins - I switch on the main batter isolator switch I can operate the PTT as normal up and down.
However after about 2-3 mins the power trim motor comes on and lowers the engine without any switch being touched.
I can stop it going down by depressing the UP switch - but the engine does not go up.
Releasing the switch and the engine lowers until it is fully down. PTT motor then still continues to try to lower the engine. Only way to turn it off is using the main battery isolator switch.
It does not happen in reverse - it only tries to lower not raise the engine.
Any ideas anyone??