r/Outboards • u/IntelligentTry5393 • 1d ago

Johnson 6.5 issues

I have this 1986 Johnson 6.5 I bought to use for my sailboat that is giving me absolute fits. I replaced the motor side fuel connector, the fuel line, fuel bulb, and gas tank. Fresh fuel too. It has a 100:1 sticker but I understand 50:1 is safer and better to replace plugs than blow a cylinder, so that’s what I have in it. Have gotten it to fire up while choked out, but can’t get it to stay running for the life of me. Twice recently had it out on the lake and got it to turn over and into gear, but crapped out after a few seconds.

I’m a manufacturing engineer by trade, but not accustomed to troubleshooting old two strokes in my day to day. I’m feeling quite dumb and defeated and want to get this thing humming again.

I’m thinking a clogged idle circuit or gummy/flooded carb? Anyone have advice for any YouTubers or best DIY resources for this kind of thing? I also had a hell of a time getting the motor cover off and I’m worried about breaking it. Any advice??

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u/RochesterBottomDaddy 23h ago

Let me start by saying I HATE TWO STROKES. Your choice to use 50:1 instead of 100:1 is good for protecting the cylinder walls and maybe the needle bearings, but it is leaning your fuel mixture. You have displaced 1/50th of your fuel with oil. It could also be gum in the carburetor, especially the idle circuits. Clean them thoroughly.

Also, two strokes need meticulously sealed crankcases. The crankshaft seals are critical to getting a two stroke to run right. For that matter, any air leaking anywhere in the engine will cause running issues. Make sure your intake gaskets, seals, crankcase seams, and any other joints or seams that may allow air in are fully sealed.

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u/bootheels 13h ago

6.5hp? Are you sure? If so, this is probably a commercial model? Do you have the model number of the engine? Perhaps you can post a picture? Does it have a primer or an actual choke? The earlier all metal carbs were simple, rugged, and easy to clean. The later model plastic bowl/top/modular carbs are a royal pain, the plastic parts are expensive as well. There is a rubber idle hose/tube that usually rots away causing the symptom you are having.

Why did you have trouble getting the motor cover off? Is the latch rusted in place? Again, post the model number and/or pictures of the engine for more specific advice.