Mercury 850 Trim Pump wiring

[Alexhandro26]

Hello, I have a 1980 Mirrocraft with a Mercury 850 on it. The engine still works great but I can't get the prop in the water. Turns out all of the wires from the motor to the trim pump etc...have corroded within the wiring jacket. The trim pump itself seams to be in good working order, I know there is power going to it but when I press the trim up and down buttons on the "dash" nothing happens. Does anyone know what the wires going from the trim pump to the motor are?

Thanks!

 

[Chris1956]

Do you have the PTT pump/reservoir in the boat? If so, the green wire will get power from the PTT pump's red wire(at the control panel), and the motor should trim down. Originally there was a trim limit switch, and pushing the middle button would trim the motor up. Those usually break, an the fix is to bypass it or simply push the middle and top buttons together to trim and tilt the motor up.

You should be able to jumper the PTT Pump power to blue for up and power to green for down, to help isolate the issue.

 

[Alexhandro26]

Thanks for your help! Yes, I have the pump in the boat but there are wires (not associated with the small wire harness that plugs in to the pump) that run in to the side of the engine mount(I believe that is where it is going....it isn't terrribly obvious). What I do know is that all of those wires running from the engine mount area to the compartment that has my pump in it are completely corroded. Now I must figure out how to get in and replace said wires.

 

[Chris1956]

OK, On your motor the three wire harness from the pump/reservoir are the ones that control the PTT. Newer models had the PTT incorporated into the motor wiring harness.

Can you make a 6" jumper wire with a male spade terminal on each end? If so, plug one end into the horizontal connector on the PTT Pump. Now plug the other end into one of the vertical connectors and the motor should spin and move the motor up or down. If you can get that to work, you can either adapt what you have or make a new three wire harness for the PTT.

 

[Alexhandro26]

Sounds great! Thank you so much for explaining it in a way that I can understand. I will give it a try in the next day or so and get back to you.

 

[Alexhandro26]

Okay, I jumped the horizontal with one of the verticle terminals and the first few times I did it I heard a click coming from somewhere on the pump. Now I can not reproduce the click. I am charging the battery to ensure it doesn't play a roll in the loss of said clicking.

 

[Alexhandro26]

Okay, I jumped the horizontal with one of the verticle terminals and the first few times I did it I heard a click coming from somewhere on the pump. Now I can not reproduce the click. I am charging the battery to ensure it doesn't play a roll in the loss of said clicking.

 

[Chris1956]

I guess it is time to jumper from battery Positive terminal to the thick blue wire and see if the PTT motor will run up. Then jumper from battery positive terminal to the green wire to see if PTT motor will run in down direction. If that doesn't work. check to make sure black motor wire is well grounded to battery negative terminal.

 

[Alexhandro26]

Eureka~ A direct from battery jump makes the PTT work! Now what? I was thinking of testing the male end of that wire harness (with the 2 vert. and 1 horiz. spades). My next question is in regards to the wires that were completely corroded that went to the side of the boat motor mount?

 

[Alexhandro26]

Another question for you. On the wire "harness" coming from the trim switches, where is the purple wire supposed to go on the PTT?

 

[Chris1956]

Well, the purple wire would go to the trim limit switch. That switch probably broke long ago. See if you can find two bullet connectors from the starboard trim bracket., where the switch is mounted. If the switch is broken, disconnect it and connect the two main harness wires together.

Back to the PTT Pump. Some had two solenoids some only had one solenoid for trimming up. It is possible that your solenoid(s) is bad. Since it isn't working in either direction, I would suspect wiring. That 3 prong connector powers the solenoid, which in turn closes like a heavy duty switch and powers the PTT motor.

 

[Alexhandro26]

I am not sure exactly what you mean by the two main harness wires? I plead ignorant. My thought was that the purple wire, not being connected to whatever it was supposed to be connected to, provided a sort of "cut-off" and that's what was making the switch not work.

Would I be able to go get some type of 3 way switch and connect it directly to the battery and run the PTT that way? At least until I can trouble shoot the switch on the control panel (it is extremely hard to get to).

Might you know of any good resources for purchasing these solenoids?

Again, I thank you for your patience and knowledge.

 

[Chris1956]

A single pole double throw switch (5A or so) would allow you to operate the PTT. The center, common post would be for +12VDC and the upper post would probably get the green wire for trim down. Blue wire on the remaining post.

The main harness wires I spoke of are the ones that run from the PTT unit to the trim limit switch and from the trim limit switch to the PTT Control Panel. It sounds like you may not have one of those.

 

[Alexhandro26]

Well, I took the kids out for the first trial in about 8 yrs and thanks to you, it happened!! I made the spdt work right in with the PTT. I wanted to attach a pic to show you but my phone takes too large of an image. I will say, you have made me happy! And my kids too