Changing motor on 80's Inline 6 Tilt & Trim pump?

[mmoncur]

Hi,

My Mercury 140 (1980 or 81) motor came with the old-style Tilt & Trim system that has 2 rams and a hydraulic pump with a square reservoir mounted in the boat, with hoses going to the rams from there.

It currently trims down but not up and I have the issue narrowed down to the motor -- everything else seems to work electrically, but when I try to apply power directly from +12V to the motor's "up" connection, bypassing the solenoid, it does nothing and heats my jumper wire up to the melting point within a second. So most likely the motor is shorted out.

There are various 3rd-party motors available from Arco, Prestolite, and API, they all include the motor and reservoir only and you attach them to your existing pump, valve body, etc.

Has anyone done this procedure? How hard is it to replace? I'd like to know what I'm getting into before I drop $100-200 on a new motor. I can also get a new entire pump assembly but that gets closer to $500.

Thanks!

 

[Chris1956]

The motor/upper reservoir is not hard to replace. There are several stainless steel screws and a spagetti gasket, which need to be removed. If I remember correctly, there are a couple of different aftermarket pump/reservoir models, which look almost the same. The difference is the length of the motor armature. Make sure you exactly match the motor armature from your original part to the replacement, or it will be too short or too long to spin the pump motor.

Alternatively, you can try a starter motor shop and see if they will repair your existing motor.

 

[mmoncur]

Thanks! I have a motor on order. It comes with the gasket / O-ring and what appears to be an extension for the armature to make it the right length. I'll compare with the original motor before I try to install it.

 

[mmoncur]

Motor and solenoid replaced, and my tilt/trim works! Thanks for the encouragement.

The hardest part was dealing with the small hole in the back of the boat the whole unit was installed behind -- that made it hard to reconnect hydraulic hoses and wires. Also, it didn't work at first due to low oil, and I had to bleed the system by moving the motor up and down (manually) 4-5 times, topping off the SAE 30 oil each time. After a few of those the pump was able to raise the engine.

I will post some pictures of the process later. Time to go to the lake!

 

[Chris1956]

Pull on the bottom of the motor. If she moves 3/8" or more, you probably need to bleed the cylinders themeselves.

 

[TheRiot]

mmoncur, when this happened to you, could you hear the motor engaging at all? I have a similar problem, but when I push the tilt or trailer button, I can hear the motor running, but the lower unit doesn't move. Thanks in advance.

 

[mmoncur]

My motor engaged in "down" but not "up" mode. When I took the whole thing apart I tested the motor and it ran (weakly) in both directions. I think the solenoid was the real problem. But I replaced the motor and solenoid anyway.

Your symptoms sound like a pressure problem - for starters, that's how mine acted after replacing the motor when there wasn't enough oil in the reservoir. Open the vent screw and the fill screw. Top off your fluid, try to raise the engine, raise it manually if you need to, try to lower it, top it off again. After I did this 4-5 times it started raising and lowering with the motor. If you don't get to that point you either have a leak somewhere (should be obvious) or the actual pump (the "valve body assembly" below the motor) has a problem.