1988 Evinrude 15hp loses Power when at full Speed

R

reeflodge

Seaman Apprentice
Joined
Apr 23, 2011
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47
My 1988 Evinrude 15hp engine is losing power when at full throttle.
It will go fast for about 30 seconds but then slows right down instantly
The engine does not cut out when this happens, it just slows right down and then it will immediatly pick up again
for another 30 Secoconds and slow down again.
Its seems to run fine at a constant medium throttle.

The carb was stripped down and cleaned only recently.
New Plugs
New fuel lines.

It was working fine all day yesterday, the problem began today.

Any ideas anyone?
 
oldcatamount

oldcatamount

Lieutenant Commander
Joined
Apr 4, 2010
Messages
1,740
Re: 1988 Evinrude 15hp loses Power when at full Speed

This could be ignition related but start by looking at the fuel tank vent. If it's not venting, the motor will bog down and then re-gain speed like you describe. It also could be an ignition coil going bad (or a bad plug wire) and thereby losing a cylinder intermittently. You can check the ignition while it's running with an inductive timing light. Intermittent flashes will lead you to the bad coil or wire.
 
kbait

kbait

Commander
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Nov 13, 2007
Messages
2,449
Re: 1988 Evinrude 15hp loses Power when at full Speed

Perhaps the float valve is closing too quickly??
 
R

reeflodge

Seaman Apprentice
Joined
Apr 23, 2011
Messages
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Re: 1988 Evinrude 15hp loses Power when at full Speed

What would cause the float to close to quickly?
 
H

Haffiman

Commander
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Dec 17, 2009
Messages
2,454
Re: 1988 Evinrude 15hp loses Power when at full Speed

Take your fuel line and put directly on the carb using the primer bulb as pump and test.
If still the same, I would guess you have a sticking float valve. When you stripped and reassembled the carb, did you remember the small spring for the needle valve that hold onto the float tab?
 
R

reeflodge

Seaman Apprentice
Joined
Apr 23, 2011
Messages
47
Re: 1988 Evinrude 15hp loses Power when at full Speed

Hi
Yes the spring was put back in place.
 
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