1989 Johnson 8HP J8RCEC

SMAYO

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Aug 6, 2008
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I am not able to obtain full power while running at full throttle unless the air silencer is removed. Plenty of power if the silencer is removed from the carburetor. The silencer is not fouled or plugged in any way. Motor starts and runs beautifully at slow speeds. This happened suddenly and not over a period of time. The carburetor has been "spray cleaned" but not removed and disassembled for cleaning. Any help or suggestions are most appreciated. Thanks, Steve
 

tashasdaddy

Honorary Moderator Emeritus
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Nov 11, 2005
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51,019
Re: 1989 Johnson 8HP J8RCEC

spray cleaning does nothing for an outboard other than removing the lubrication off the internal moving parts. http://forums.iboats.com/showthread.php?t=244013

parts diagrams here http://shop2.evinrude.com/ext/index.aspx?s1=bf6ad09c53cead335fcfd8a6471c0f7f


(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.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

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.
 

iwombat

Captain
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Jul 12, 2006
Messages
3,767
Re: 1989 Johnson 8HP J8RCEC

By removing the air silencer you're leaning it out a little. You might want to look at your primer and see if it's leaking some. Other than that, I'd say a thorough carb cleaning is in order paying special attention to the high-speed jet.
 

SMAYO

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Aug 6, 2008
Messages
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Re: 1989 Johnson 8HP J8RCEC

Many thanks for your suggestions. I'll give them a try.
With appreciation. Steve
 
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