Trim runs on its own.

[Kevin Crandell]

I have a 2014 Mercury 75 hp outboard. Has tilt on throttle and side of motor. It has developed a nasty habit of trimming up or down on its own. Doesn't stop went it reaches up or down. Shouldn't be a moisture issue, it's hot and dry here, 100+ today. I have taken the throttle apart and there is a thin plastic pc. that slid back into the switch and fixed the problem. For a day. Not sure how to get the trim thumb control out of the handle, in hopes that is the problem. Any tips on getting the trim switch out?

 

[Texasmark]

6 years of age seems to be a bit early to have problems as I will mention, but usage/care goes a long way in unleveling the playing field. Moisture could have gotten into your switch and made an internal path across the contacts, or the contact material may have worn off to the point that the dust has made a path across the contacts. Relay contacts may have become pitted from excessive usage and pitting reduces the contact area meaning that the points that do make contact, get hot enough to weld together and remain connected when power is removed.

Easiest fix is to swap relays and see if the problem follows the relay. Otherwise it's replacing the switch.