115 johnson fuel injected 1998

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larry h

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fuel injected johnson 115

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motor stumbles while rpm coming up (under load) ... (around 1500rpm) sometimes. compression 150 lbs on all cylinders except one 121 lbs. 118 hours on motor. any ideas ?
 
iwombat

iwombat

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Re: 115 johnson fuel injected 1998

Yeah, there's something going on in that low cylinder. You done a decarb recently? If so, move on to inspecting the plug. Does it look like it's been steam-cleaned?
 
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larry h

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Re: 115 johnson fuel injected 1998

Had a issue with a cylinder tht actually cracked the porcelin on the plug tip... replaced plugs ran great for a short time 2 hours now having issues again. have not de carb anything as of yet ....
 
iwombat

iwombat

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Re: 115 johnson fuel injected 1998

118 hours is probably getting due for a decarb. Were the heads ever re-torqued after initial break-in?
 
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larry h

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Re: 115 johnson fuel injected 1998

Heads were re torqued after break in... i run oem additive in fuel to keep carbon from building up...
 
iwombat

iwombat

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Re: 115 johnson fuel injected 1998

30psi difference is concerning to say the least. I'd try a full decarb procedure (read the FAQ and pick a method you like) and retest the compression. If it doesn't change I think its time to pop the head off and take a look-see.
 
iwombat

iwombat

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Re: 115 johnson fuel injected 1998

Also, what about those plugs? Does the one in the low compression hole look cleaner than the rest?
 
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larry h

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Re: 115 johnson fuel injected 1998

all plugs look the same .... except for the cracked porcelin . Woulded that be a heat issue( lean ) ?
 
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