1991 Johnson Compression Problem

[towens]

I have a 1991 Johnson 90 HP. I suspected carb problems late last fall. When I got it to the shop this winter I found out I have 2 cylenders at 75 the other 2 at 120. My mechanic says several thousand to repair. Or just mix the oil in the tank and run it as long as I can. The boat still runs great when it warms up. Are their any lubricants that will help compression at all?<br /><br />TOBOCO

 

[jgrisham02633]

Re: 1991 Johnson Compression Problem

Are the two low compression cylinders opposed or on the same side of the motor

 

[jgrisham02633]

Re: 1991 Johnson Compression Problem

If they are on the same side wich is not likley, you can throw on a special low compression head gasket to bring the compression up a bit.

 

[towens]

Re: 1991 Johnson Compression Problem

Unfortunately they are opposed

 

[reeldutch]

Re: 1991 Johnson Compression Problem

they better be opposed otherwise it wouldnt be a carb problem.<br />if it was my motor i would repair it now before you do some real damage like trowing a rod trough your block (not likely but possible)<br />doing some major bearing crankshaft damage.<br /><br />you can run it till it realy breaks but i would find out the cause and rebuild it before more damage happens.<br /><br />my bottem carb was running lean and destroyed the bottem pistons and cylinders.<br />after about 1500 dollars a lot of fun and learned a lot i got a motor i know.

 

[DHPMARINE]

Re: 1991 Johnson Compression Problem

toboco, I missed the step where the heads were pulled for inspection.How did the pistons/cylinders look ? And the head gaskets ?<br /><br />DHP

 

[towens]

Re: 1991 Johnson Compression Problem

My mechnanic did not pull the heads. He just told me that the compression was not good in 2 Cylinders and that it was going to be an expensive fix.

 

[rodbolt]

Re: 1991 Johnson Compression Problem

without pulling the heads at a minimum he cant make a guess much less an estimate. pull the heads for inspection. could be a blown head gasket. could be bad rings/cyl walls. but I am afraid were I you I would find another mechanic.