Mercury 175 trim problems

[tmrayhart]

I have a 1996 Mercury 175 EFI. I went fishing and after coming home and putting the boat away, I awoke the next morning to find that the motor had trimmed all the way up. The trim kept running all night and melted the solenoid. I had the wiring harness replaced and the solenoid and was reassured that this happens to motors about once in a lifetime. Well it happened again, except I caught it before it fried everything. My question is, what is making it trim up? I was told that the trim switch might be bad.. Could this be the culprit.?

Any insight would be wonderful.. Thank you

 

[Barnacle_Bill]

Re: Mercury 175 trim problems

Yes, the switch could be bad.

 

[j_martin]

Re: Mercury 175 trim problems

You said you went fishing. Most bass botes have 2 or 3 other switches wired into the trim circuit. It could be any of them.

Usually when a switch is getting so flakey, it will feel a little different, or be touchy in some way.

 

[tmrayhart]

Re: Mercury 175 trim problems

Every switch feels solid and doesn't seem in bad condition.

 

[j_martin]

Re: Mercury 175 trim problems

The other thing they do is chop into the main control harness, violating the outer water tight cable jacket, and usually using idc, crimp, or other dry only splices. Add a mouse or two, and walla --- mystery movements.

Just for grins and giggles, slowly move the shift lever back and forth, and listen closely for any action in the trim solenoids. The wiring follows a pretty tortuous path through the control set.

 

[sschefer]

Re: Mercury 175 trim problems

Just walked in from the shop, read this post and started laughing...

The same dang thing just happened to me not more than 20 minutes ago.
Mines a 99 two wire with relays and and I had it on the bench after rebuilding it. One of the relays was bad. When I shook it, the trim went up by itself. If you're 96 is a two wire with relays, you might want to check the relays. They run about 11.00 each and I use them for my fuel pump so I had a spare. Fixed the problem with mine.

Aint that the dangedest coincidence...