Johnson 85HP Power Loss
have a '78 Vandal with a '78 Johnson 85 Hp motor on it. The boat ran well
for the last 5 years. Fired right up every time. This past summer I ran it
pulling friends on a tube and as I did the power in the motor got weaker
until eventually it got to the point I cannot start the motor. Do you have
any recommendations on what I can do to get this running again.
Sorry to be the bearer of bad news, but it sounds like your motor seized.
This is most likely the reason for the slow power loss, and now the fact
that it won't start at all. I would suspect that the piston rings on this
motor were stuck and that caused one or more of the pistons to fail. This
motor was designed around the time when our fuels were much different than
we have now. It is very susceptible to sticking rings, just because of the
way the piston was designed back then. The newer fuels do not have much
detergent in them, so the older motors don't last long. I would recommend
rebuilding it with newer designed pistons in all 4 cylinders. Go through
all of the components and make sure you replace the water pump. You will
have a good reliable motor after all this, but be prepared as you will
have a lot of parts to buy. Good luck on your rebuild.
Please submit whatever questions you have to IHRTechTalk@yahoo.com. All questions and answers selected will be displayed on this page as they come in. Note: though all boaters are welcome, priority may be given to I.H.R. members. Randy can not be held responsible for any advice given. Though his information and expertise is second to none, he has no control over what you do with your boat. It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.
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