75 HP Mercury Bow Trim Up Does Not Work

[Badger48]

I have a 75 HP Mercury (will get model/year tomorrow morning) on a 1984 Larson Manta 5000 that will not trim the bow up. Bow down and trailer up both work fine. Hoping this wiring diagram can help someone help me. I did clean the connections between the switch and harness in the first (throttle wiring) picture. I've attached some pictures but let me know if the wiring descriptions are hard to read. Thank you in advance for any help!

 

[alldodge]

Purple/White is main power feed to trim switch

Since trailer up works, and trim up doesn't, your problem should be the switch it self. Pic shows Purple/Red instead of Purple/White

 

[BWR1953]

I had to replace the trim switch on my throttle handle. It was just old, beat up and worn out. (I can relate to that! )

Mine is a 1985 Mercury 50HP with the Commander side control box. The switch part number is: 8M0046008

I had to slightly enlarge the hole in the handle a little in order to get the switch to fit, but it was easy to do.

 

[Badger48]

Thanks alldodge and BWR1953, I'll start with replacing that switch. (And I hear ya BWR1953, wish it was as easy to replace beat up parts on us as it is on the boats)

Any idea what the brown/white wire is for and why it is not connected to anything? Should it be grounded to something, or do I just leave it disconnected?

 

[alldodge]

The Brn/Wht goes between trim gauge and sender. You have a gauge?

 

[Badger48]

Not that I'm aware of. Would it be worth it to install one? It's a small enough boat that I can get by without it I'm guessing, but if it's not too hard or expensive to install then why not

 

[alldodge]

Most OB don't need it, mainly I/O
Would also need the sender on the leg of the OB

 

[Badger48]

Ok, so pass on the trim gauge/sensor. I was able to fully disassemble the bow switch and clean the very dark contacts on it. Everything works like a charm now. Sorry for the spam posts/edits, but hopefully it helps someone somehow in the future. Thanks again @alldodge and @BWR1953

I removed the switches completely and tried some testing. In this picture, if I touch blue to brown it goes up, and if I touch purple to brown it goes up. But nothing will make it go down. I'm thinking something is messed up in the "Rear Wiring.png" picture from my first post.

Just realized if touched green to brown makes it go down.

Swapped green and purple wiring and now purple makes it go up but green will not make it go down. So definitely the switch it seems.

It's a Quicksilver throttle. Motor is 1984 Mercury 75 HP Model 1075624

 

[alldodge]

The switch should work opposite of wire position because the contacts slides opposite of the toggle on top

Blue/White up (think of the sky)
Green/White down (think of grass)
Brown/White would be main 12V power feed to the switch

With down not working, then it could be a connection or a relay

Have not seen 4 wires on a trim switch unless it also has a trailer function
Your first listing states 2 Blue/White wires, is this correct?

Try to connect the purple/white with the green/white

 

[BWR1953]

Ok, so pass on the trim gauge/sensor. I was able to fully disassemble the bow switch and clean the very dark contacts on it. Everything works like a charm now. Sorry for the spam posts/edits, but hopefully it helps someone somehow in the future. Thanks again @alldodge and @BWR1953

I removed the switches completely and tried some testing. In this picture, if I touch blue to brown it goes up, and if I touch purple to brown it goes up. But nothing will make it go down. I'm thinking something is messed up in the "Rear Wiring.png" picture from my first post.

Just realized if touched green to brown makes it go down.

Swapped green and purple wiring and now purple makes it go up but green will not make it go down. So definitely the switch it seems.

It's a Quicksilver throttle. Motor is 1984 Mercury 75 HP Model 1075624

Yup, that's the same as my throttle.
Glad that you got it worked out!