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My 1976 Johnson 6hp outboard idles OK,but won't rev up to power under load when I open the throttle. When I checked the spark pluge, I found the top one to be wet with fuel mix, but the bottom one was normal, black and sooty, but dry. Changing plugs didn't help, same situation on the new plugs. I disconnected the top plug wire, but then the motor wouldn't start at all. Is it possible the top plug is firing at low RPMs but not at higher speed? HELP?

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High speed jet in carb is blocked disassemble carb remove jets and dip jets and carb assm in carb cleaner ( it comes in a gallon can with a parts tray in the can ) available in most autoparts stores BEWARE remove all Rubber O-rings and gaskets before dipping let set overnite or a couple of hours then blow parts off and reassemble. as far as adjustment screws just turn then in until they stop and count the turns then remove them. When reassembleing just reverse the procedure insert turntil they stop then back them out the number of turns that you wrote down. I had to do this with a 1985 150hp V6 with six carbs and it fixed all my problems as well as a 1976 25hp Johnson. Good Luck

Posted on Aug 06, 2009

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Check for spark against the block. they sell a test kit, i think harbor freight sells one, where you hook it in line and should be able to see if it is firing or not.

Posted on Jul 29, 2009


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Hey Pete.. this sounds serious.... will it rev up while in neutral? If it revs freely and high.. the power head should be ok.. if it will NOT rev up freely and high.. STOP - you are causing more damage..
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