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1996 Johnson 25 hp HJ25RAEDA motor surging

M

mark_lilley

Member
Motor runs at less than full revs (guessing 4500 - 5000) at wot but surges to full revs and immediately down again. The surge is fairly consistent, probably every 10 secs and usually occurs after about a mile at wot. I have:-
1) statically checked resistances across all coils as I do not have a peak reading voltmeter, which check out ok.
2) Stripped carb and cleaned main jet and bowl
3) Vented fuel tank manually while travelling, when this occurs
4) Squeezed primer bulb while underway
without any joy.
Any assistance would be greatly appreciated.
Thanks, Mark
 
Re: '96 Johnson HJ25RAEDA motor surging

A typical fuel related problem.
Cleaned 'jet and bowl', but did you check out the needle valve?
Try the following:
Connect fuel hose from tank directly at the carb, by-passing the pump. (Use the primer bulb as pump). -Test.
If ok -fuel pump or air-leak in connector++++
If still a problem, dismantle the carb TOTALLY and check fuel flow through needle valve etc.
Be sure to get the float-high correct.
 
Re: '96 Johnson HJ25RAEDA motor surging

Thanks for the response Haffiman. I will strip and clean carb as suggested. I was getting concerned that it was perhaps the powerpack. When carb is inverted the bottom of the float should rest flush with the flange, is this correct? Thanks again
 
Re: '96 Johnson HJ25RAEDA motor surging

"When carb is inverted the bottom of the float should rest flush with the flange, is this correct?"

Yes!
Remember to remove the needle seat when cleaning. It might be a small piece from a fuel hose partly blocking.
You may get an indication if doing the following.
Remove the carb and hook up the tank hose.
remove the drain screw. (If a primer solenoid outlet, just leave it open)
Holding the carb in correct position and carefully squeeze the bulb you may monitor the fuel flow leaking out(You may even do this without removing the carb, watch for fuel spill!)
 
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