65 hp Johnson won`t idle or run properly

[Sheltering]

I have a 1993 Johnson 65 hp outboard. I purchased boat (16 ft Bayliner) & motor last fall and never really had a chance to test it until now. Outboard would not idle nor run properly.
I removed and cleaned all three carbs, but still had the same problem. I took boat and outboard to a boat shop, thinking that I needed a more experienced person to adjust the carbs. After $325.00, I was told by the shop that the motor was surging and that I probably needed to replace the stator. I took the boat as it was and put it in the water only to discover that it was working exactly the same as before the shop. After one hour of attempting to get the motor to start and idle, I switched fuel tanks to one that had high test gasoline, and discovered that, after a while, it started to idle and run pretty good. I now finally had the courage to venture beyond the dock and after about one hour it was still running ok.
Is it possible that I have a bad stator and that the higher octane gasoline is compensating for a weaker ignition, or is it that this outboard will only run on the higher octane gasoline?
Any advise would be greatly appreciated.

Don in New Brunswick, Canada

 

[fireman57]

Re: 65 hp Johnson won`t idle or run properly

Actually, these engines were designed to run 87 Octane. Higher than that you can actually damage your engine from predetonation of the fuel. If it ran fine I would suspect something in your tank. Run a can of Seafoam in a tank of fresh fuel. It will clean everything out. If I remember right there is no adjustment on your carbs they are fixed jets.

 

[Silvertip]

Re: 65 hp Johnson won`t idle or run properly

Actually, these engines were designed to run 87 Octane. Higher than that you can actually damage your engine from predetonation of the fuel. If it ran fine I would suspect something in your tank. Run a can of Seafoam in a tank of fresh fuel. It will clean everything out. If I remember right there is no adjustment on your carbs they are fixed jets.

Not quite the way it works. High octane fuel prevents detonation. Higher octane actually is less volatile than regular which is why it is recommended in high compression/high performance engines that require lots of spark advance. So the answer is NO! The difference in fuel is not the reason it began to run better. The old fuel may have been the issue. Since it seems to be running better, load it up with Sea Foam (a fuel system additive) or any similar product along with fresh fuel. If no further improvement is noted, then there may be other issues. Just don't start throwing parts at the problem hoping you get lucky. That is very expensive troubleshooting technique.

 

[fireman57]

Re: 65 hp Johnson won`t idle or run properly

Silvertip you are right. I had it backwards. Guess my fingers type faster than my brain can get it wrong!

 

[Sheltering]

Re: 65 hp Johnson won`t idle or run properly

Thank you for your quick response.

There is one mixture adjustment screw on each carb.

Actually the tank I switched from was fresh regular fuel (mixed 50:1), and I am sure that both tanks were clean before filling. Your response that I should be using 87 octane makes my dilemma even more puzzling.
Although it now `runs`, it is still quite rough at times. Should I be considering a defective stator? Is there a way that I can test the stator?
I had already installed new spark plugs and checked the compression (120 psi on all three cylinders).

Help please!

 

[pn]

Re: 65 hp Johnson won`t idle or run properly

please dissassemble your fuel pump and clean.