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89 johnson 15hp cuts out! help!

aselti618

New member
just picked this motor up,

fires right up. idles good. free revs all the way up high with no load.

I have replaced the plugs as well as the little timing adjustment wheel.

after I leave the launch, it winds up to just over half throttle and acts like it wants to shut off. when I back off the throttle it immediately perks back up.

is this a carb issue?
 
Okay, there's no discoloration of any kind on the head. I don't believe it's overheating. What would the plugs look like if there was water on them?

Wet like fuels on it?
 
Regular water would look like small drops/beads... it does not of course mix with gas nor oil so it should be pretty easy to find if it's there.

Salt water would look like extremely small fried BB's on the electrodes.

If you have compression and spark.... the usual cause of your problem would be a fouled carburetor... OR... one that's out of adjustment.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
Caution do not rev high rpms in neutral without a load on the engine,prop. pushing water. Damage will result. $$$$ Follow joes advice. If no results from fuel diagnostics try a compression test on all cylinders, Then a spark test!
 
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