Mercury 850 Thunderbolt - seized pivot

[braided line]

Hi guys

I recently purchased a half cabin fishing boat with a Mercury 850 Thunderbolt outboard. I think it is of mid 1970's vintage.

It has suddenly become very stiff to turn. I have changed the steering box and cable, but the problem is with the pivot on the motor.

My mechanic has heated it and pumped heaps of grease through the nipple. When it is heated, it turns really easy, but seizes up again as soon as it cools.

My mechanic suggests that there is nothing else that can be done without pulling it apart. He tells me that it is a big job and would not be worthwhile in such an old motor.

Anybody else have any tips?

Much appreciated

Mick
Melbourne, Australia

 

[Yepblaze]

Re: Mercury 850 Thunderbolt - seized pivot

Continue as the mechanic did by heating and getting lube in there while moving back and forth, or tear it down and fix it.

 

[Chris1956]

Re: Mercury 850 Thunderbolt - seized pivot

Mick, That motor has an upper and a lower bushing. See which one is not getting lubed and concentrate on that one. Normally the top one is the one that doesn't get lubed well. If so, tilt up the motor all the way. Now tie a piece of rope under the Antiventilation plate and around the transom clamp. Put a stick in the loop of rope and twist it like a touirniquet. At the same time rock the motor on its pivot point. The intent is to get the motor to move up on the pivot shaft, and open up the top pivot. Now pump some grease and use some heat to lube it up.

Tearing down the motor requires that you remove the LU and the powerhead, and dissassemble the midsection, working around the corroded bolts, w/o breaking them.

 

[braided line]

Re: Mercury 850 Thunderbolt - seized pivot

Thanks Gents

I will give it a try and let you know how I go.

I am hopeful that the last suggestion works, as the grease only seems to be getting to the lower bushing (thbis is where the grease comes out).

Great site, great advice, much appreciated. I will put my mechanic onto this site!

Mick