New Mercury 115 wtih trim problems

[MarshAggie]

I have a new 115 Merc on a pontoon boat that I keep in the water. When not in use, I normally trim the motor up just far enough to get the skeg out of the water. Always concerned about bringing it all the way up an cracking the cowling. A few weeks ago, I took a look at it and the motor was mysteriously trimmed up all the way (no cracked cowling though). When I tried to trim it back down to the usual position, the battery was dead.

As soon as I plugged in the charger, the motor started trimming back down on its own. When I hit the toggle on the throttle, I could stop it from going down but couldn't make it go up. When I let go of the toggle, it continued back down. It wasn't until I hit the toggle on the cowling that I was able to stop it.

Since then, I haven't been able to duplicate the problem. The boat is currently in the shop and they can't duplicate it either.

I'm convinced that, on its own, the motor started trimming all the way up and eventually ran the battery down.

I'm at a loss to figure out what needs to be replaced. The toggle switch on the throttle "feels" right.

Any thoughts?

 

[guyjg]

The "up" circuit has/had a short that provided 12 vdc to the trim motor. Suspect a stuck trim up relay...contacts could have welded (blue wire) or the relay socket has some corrosion or debris. Switch relays from up to down and see if it occurs again in the down circuit. If it does then the relay needs replaced. I normally replace both relays at the same time but since the engine is new replacing the one is fine.