rpm problem

PeterMark

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Joined
Jun 5, 2008
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16
I have a 1996 johnson 130 looper and on a recent trip I was returning to the dock at wot 5500rpm and all at once i droped down to 4500 rpm, engine ran fine, no alarms, but would not run past 4500. Engine would surge from time to time but that was all. When i got home noticed one of the spark plug wires was nearly burned in two so i replace all wires and plug, next trip same thing only run at 4500rpm. Came home replaced fuel filter, flushed lines, install fuel pump repair kit check all hoses and next trip did same thing. Any ideas of what to check next?
 

PeterMark

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Jun 5, 2008
Messages
16
Re: rpm problem

I haven't used the gap tool but I pulled each spark plug wire off 1 at a time and the engine seemed to bog down. So I'm at least getting spark and the engine really runs well and idles fine, it's not until you put the engine under full load at wot that the rpm is only at 4500.
 

wilde1j

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Apr 15, 2002
Messages
5,964
Re: rpm problem

Have you checked to see if the carb throttle plates are horizontal when throttle is fully forward? (Do with engine NOT running - you should rotate prop while shifting and moving lever fwd).
 

PeterMark

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Jun 5, 2008
Messages
16
Re: rpm problem

Yes, the carbs seem to be opening fine, I have checked it with the engine running as well, seems to be getting plenty of fuel.
 

wilde1j

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Joined
Apr 15, 2002
Messages
5,964
Re: rpm problem

Try squeezing the primer bulb when the RPM sags. If RPM picks up, you can be sure it's a fuel problem.
 

PeterMark

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Joined
Jun 5, 2008
Messages
16
Re: rpm problem

That's really about it, I checked and tighten all fuel line connections, new fuel filter, used back-up prop still same, also disconnected VRO and mixed fuel in the tank, still no difference. I'm running out of things to check and hate to take it to the dealer.
 
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