power trim issues

[rjnitro101]

i have a 115 merc 96, have an issue with power trim,i was out boating,i noticed the volt guage went from a normal 13 to 18 for a short time, then a few minutes later, the motor started triming up all the way while running, i shut it off right away, but the trim wouldnt stop till battery power was disconected. narrowed it down to i thought, the trim switch on the control i replaced it. left power hooked up,came out of the house and the trim was engaging with the boat, in my driveway, any suggestions on what would cause this or a possible fix

 

[valor]

Re: power trim issues

Sounds like it may be the remote switch (under dash / at throttle) . My 92 115 was doing similar but was lowering as well as cuttiing out. It turned out to be a faulty switch - shorting out. Failing that, it may also be the solenoid switch on top of the trim unit itself, although this is unlikely. The first would be first to check and troubleshoot from there.

 

[Thoroughbred]

Re: power trim issues

i have a 115 merc 96, have an issue with power trim,i was out boating,i noticed the volt guage went from a normal 13 to 18 for a short time, then a few minutes later, the motor started triming up all the way while running, i shut it off right away, but the trim wouldnt stop till battery power was disconected. narrowed it down to i thought, the trim switch on the control i replaced it. left power hooked up,came out of the house and the trim was engaging with the boat, in my driveway, any suggestions on what would cause this or a possible fix

This EXACT thing happened to me last month and was searching how to fix it when I cam across your post. Mine is a 1997 Merc 150 Offshore. I had a battery go bad so I replaced it (I have duals). Ran it at home (in water tank) with no problems for about 30 mins total. About half way through my vacation I noticed the volt meter would go up to 18 but not while idling. Then one day the trim went up on me and I had to do the same thing as you did, three times to get back to port. I cleaned connections etc and everything worked fine except the volt meter kept going up until I went to load the boat back on the trailer 7 days later. Both trim switches were dead and we had to manually release the pressure to get the motor up.

Any and all help as to what got yours fixed would be greatly apprciated. I want to get my son back on the water. Thanks

 

[hkeiner]

Re: power trim issues

One way to troubleshoot is to use a multimeter and a good understanding of the wiring diagram for your trim system to systematically locate the problem. For example, knowing if you have ground at a location where there should not be ground, 12v at a location where there should not 12v, continuity where there should not be continuity, etc. would narrow down the problem area. Below is an example wiring diagram and troubleshooting guide (for my 1996 150HP) which may be usefull to get you started. The shop manual for your motor, of course, would be the better source for this information.

 

[j_martin]

Re: power trim issues

Mice and the furry tailed ones, chipmunks and squirrells have a way of wrecking havoc with the rat's nest that goes for wiring in the average bass bote.

Also, the auxiliary switches are usually shielded from water and splash, even immersion with a rubber boot. they split, letting water into the switch, which eventually fails.

I believe, if you pull the harness connector apart, you should be able to run the trim up and down with the switches on the starboard side of the cowl. If that works, troubleshoot the boat wiring now that it's disconnected.

hope it helps
John

 

[Thoroughbred]

Re: power trim issues

My issue ended up being a corroded wire that runs from the trim motor up into the cowl. I found a kit with connectors and shrink wrap tubing that are used on home well pumps in Home Depot. Worked great and I know it will be water proof.

Thanks for the help