Mercruiser I/O wont trim up, trailer works, help?

newc048

Seaman Apprentice
Joined
Jun 28, 2011
Messages
41
Just purchased this boat a few days ago and just like the title says, the trim up button on the throttle lever does not work but the trailer does. Now i know they both control the same movement, but trailer allows the outdrive to go higher than the trim up button which can be bad on u-joints if it gets up too high.

What would be the cause of this and is it an easy fix? I am a pretty handy guy and would like to avoid paying a shop to do this as i have quite a bit of automotive mechanical background but this is my first time dabbling into boat mechanics.

Its a 1989 Rinker 186 with a 4.3 Mercruiser I/O

Any help is appreciated!

Thanks!
 

bds85466

Petty Officer 1st Class
Joined
Jun 11, 2007
Messages
375
Re: Mercruiser I/O wont trim up, trailer works, help?

that's a pretty classic symptom.

there's plenty of posts on here with troubleshooting techniques and manuals for this. just search for em.

most likely a trim position or limit switch that has gone bad or wire broken/corroded through.

does your trim position gauge read out? you can still use your trailer button to achieve your trim needs, but you're right, you need to watch how high you run your trim when the boat is running, especially at non idle rpms.
 

MSRTBUDWISER

Cadet
Joined
Jul 8, 2011
Messages
24
Re: Mercruiser I/O wont trim up, trailer works, help?

We have the same problem on our Trophy w/ A1 outdrive, we just haven't fixed it yet because we just sue the trailer button to go up. We run it all the way down, so we don't worry about u-joints. It's either the switch on the shifter, or the terminal for the up on your pump solenoid is corroded and not making good contact... Id look there first. ~Happy Boating!~
 

paultjohnson

Lieutenant Commander
Joined
Jul 29, 2010
Messages
1,560
Re: Mercruiser I/O wont trim up, trailer works, help?

We have the same problem on our Trophy w/ A1 outdrive, we just haven't fixed it yet because we just sue the trailer button to go up. We run it all the way down, so we don't worry about u-joints. It's either the switch on the shifter, or the terminal for the up on your pump solenoid is corroded and not making good contact... Id look there first. ~Happy Boating!~
IDK about that, mine always fails at the swith on th drive.
that's a pretty classic symptom.
most likely a trim position or limit switch that has gone bad or wire broken/corroded through.
.

X2 The trim limit switch on the port side of the drive would be my 1stt suspect as well. Its underneath little round black cover thats over the hinge pin. My 86 needs to be babied every few years, take the cover off and see if there is water/corrosion in the switch . The wires down there go thru hell as well, under water and getting flexed all the time when ya turn, tilt, trim the drive. Read up on it as suggested. BTW the cover over the hinge on the stbd side , covers the trim level sending switch to the dash, [if ya have one] Or its just a dummy cover. Hopefully you can get it cleaned up and working as replacing the trim limit switch wiring is rather involved. The switch itself is easy enough. Its running the wires up thru the transom that's a PITA
 

bds85466

Petty Officer 1st Class
Joined
Jun 11, 2007
Messages
375
Re: Mercruiser I/O wont trim up, trailer works, help?

Its running the wires up thru the transom that's a PITA

you'd think there'd be a better way....I mean I'm not a grand ancient supreme mariner with a squeeze of lime, but I swear there's at least 1 to 2 posts on the front page for this issue every time I come on.

I think that's why a lot of people just live with it too. I've had my 'trim up' button not work for the life of my boat. Funny enough, right after I had my trim electronics redone last year, it quit working after like 3 days! Luckily I got the sender/gauge working to see where I'm positioned at all times.

Could be wrong, but if I understand correctly, when that limit switch fails, it defaults to the "all the way up" reading. So your electronics *think* you're all the way trimmed up, not allowing your up button to move the LU.
 

paultjohnson

Lieutenant Commander
Joined
Jul 29, 2010
Messages
1,560
Re: Mercruiser I/O wont trim up, trailer works, help?

Remember , there are two switches. The trim limit switch [port side] does just that. It limits the amount of trim available. When it hits the preset point, the contacts, no longer touch, opening the circuit, stopping it from lifting a further. When my LIMIT switch fails. My LIMIT button on the shifter is just plain dead. Trailer button still works though The trim POSITION switch, just sends a signal to the dash gauge. I dont have a dash gauge, so I am not very familiar with that part. I dont know how it defaults. In my mind[whats left of it anyhow] They appear to be unrelated [limit switch and sending switch] I shouldn't comment on that though , cuz I just don't know, no experience with sending switch.
 

stonyloam

Vice Admiral
Joined
Mar 13, 2009
Messages
5,827
Re: Mercruiser I/O wont trim up, trailer works, help?

Pretty easy to diagnose: If the trailer works, the trim up solenoid is OK. Locate (near the stern) the two black wires from the trim limit switch (port side), one goes into connector with a purple/white wire, the other into a connector with two blue/white wires. Unplug and jumper between the two connectors. Try the trim switch, if it works, bad trim limit switch or wires. Does not work, control handle switch or wire is bad. You can use it with the jumper just be careful, same as trailer now. Good luck.
 

juels98

Seaman Apprentice
Joined
May 17, 2010
Messages
37
Re: Mercruiser I/O wont trim up, trailer works, help?

Thank you stonyloam for being concise and right on with your post. This is how things should be fixed-- a test proves what doesn't work and the correct part replaced.

So the test lead me to the trim limit switch. I opened it up and cleaned the contacts (with sand paper not alcohol :( ) anyway, that revived the up trim!!!!

Now my question is the whole inside of the limit switch was covered with green/yellow grease. Can someone tell me if it's a special type of grease or any dielectric grease would work?

Also, I initially ended up following another post and changed the trim relays (guess won't have to do that any time soon :) ) I know all the other connections/terminals in the boat seem to be covered by either black or brown paint. Is it for anti-corrosion purposes or spark prevention? Can anyone suggest what paint I should get? I have access to West Marine here and some local marinas. I'm in MN!

Thank you!!

Julian
 

Failproof

Petty Officer 1st Class
Joined
Sep 26, 2011
Messages
273
Re: Mercruiser I/O wont trim up, trailer works, help?

I use dialectric grease in my trim sender. May not be correct, but thats what i use.
 

Duckmnn

Cadet
Joined
Apr 21, 2011
Messages
7
Re: Mercruiser I/O wont trim up, trailer works, help?

same problem I had.My wires were broke in helm control. rewired soldered and shrinked tube works great.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Mercruiser I/O wont trim up, trailer works, help?

Thank you stonyloam for being concise and right on with your post. This is how things should be fixed-- a test proves what doesn't work and the correct part replaced.

So the test lead me to the trim limit switch. I opened it up and cleaned the contacts (with sand paper not alcohol :( ) anyway, that revived the up trim!!!!

Now my question is the whole inside of the limit switch was covered with green/yellow grease. Can someone tell me if it's a special type of grease or any dielectric grease would work?

Also, I initially ended up following another post and changed the trim relays (guess won't have to do that any time soon :) ) I know all the other connections/terminals in the boat seem to be covered by either black or brown paint. Is it for anti-corrosion purposes or spark prevention? Can anyone suggest what paint I should get? I have access to West Marine here and some local marinas. I'm in MN!

Thank you!!

Julian

It's not paint, it's liquid neoprene... And it's anti corrosion...

Just a good dielectric grease will do the job... If you don't have any, just use a good marine grease. Any grease is better than none...
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,092
When i run a wire from positive battery to the pump it will trim the motor up and down. Any suggestions?
That tells you you have no power to the pump thru is main battery wiring.'
sounds like your missing the positive feed and that should go thru a 90A fuse link.(white plastic block)
 
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