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Need help with my 1985 6hp Johnson

S

SpencerH

New member
My name is Spencer and I have an 85 6hp Johnson that is only running 1/4-1/2 speed. I and still new to working on outboards but I have done a lot of work on this motor including; new gasket set, new gear oil, rebuilt fuel pump and carb, new fuel lines and tank, new spark plugs, new impeller, checked for spark and new plugs among various other things. All of this work work was done over 2018 winter and the motor still runs 1/2 speed at the most. Hoping someone can give me some insight.

Thanks so much,
spencer
 
Seems similar problem that i had in my 3hp Evinrude, before i did complete engine rebuild. My biggest problem was one bad piston ring, also cylinders was quite glazed. I think that compression test would be good to do, so you can be sure if there is problem with that. If you have compression problem, then there is likely problem with piston rings and/or cylinders. You told that you have already put new gaskets, did you clean all old gasket-material away from the cylinder head and cover, before putting new gasket? Did you use right torque on head bolts?
 
Thanks for getting back to me so quickly. I did not use the right twerk on the head bolts because at the time I did not have a proper maintenance manual, but now that I do I will check those first. I am fearing that u may be right I may have to tear the entire powerhead down to replaced the rings or some bearings. Not sure how much money it will be worth to dump into this motor. Also sure what the compression should be? When I did a compression test over the winter both cylinders were around 50psi and that seems low.
 
Was it ever overheated? You can usually tell by the paint discoloring on the head and exhaust side of the cylinders. That is low compression, but I always wonder about the gauges that are out there today.....and how accurate they really are. Testing should be done with a slightly "juiced" cylinder......the situation you would find with a fuel charge in it and ready to fire. All spark plugs should be out and then spun over with a nice brisk pull. Full compression should be reached by the 5th pull.
 
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Timguy; It doesn’t look like it was overheated and I have always had a strong stream of cooling water while running. And thanks for the info about checking compression I will do it again.
 
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