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1978 Evinrude 25hp loss of power after pwrhd swap

S

Semirude

New member
About a year ago I replaced the powerhead on my outboard. My old powerhead cylinders were around 85psi and the new powerhead had about 120psi. I thought, great, I should gain a little speed and maybe at the least maintain speed while carrying more weight.

Problem is I ended up losing about 5mph. The engine also coughed a little at startup, something that never happened with the old powerhead. I ran the boat for about 4 months then pulled it out of the water. I checked around the engine and found a significant amount of fuel has been coming out from the front of the carburetor.

I seem to believe the powerhead came with a reed plate and I left it in place. Other than trying to swap that around, are there any other possibilities I should I investigate?
 
Might be running on 1 cylinder.----Fuel pump diaphragm might be ruptured.----Float / float valve issues.-----Water pump impeller replaced about every 5 years ?------Check flywheel key as well.
 
Thanks for the quick reply!

I can confirm it is running on both cylinders.

I’ll double check the float and clean out the carb and jets when I pull it to change out the reed plate. Could possibly be a slightly clogged jet, especially because it took me a couple months to finish the swap.

Water impeller just changed when I did the pwrhd swap.

Flywheel key was not damaged when I did the swap, but I have been concerned about the timing, so I’ll pull the flywheel while I’m doing this to check it out as well. Great idea here!
 
I was thinking this could cause the sneezing issue along with the leak of fuel out the front of the carburetor. If the leafs aren’t adjusted right they may not be fully holding their check valve purpose.
 
Okay, reeds look fine, most are tight with only a couple where you can see a little bit of light passing through, but definitely no more than the allowed .010”.

Fuel pump diaphragm looks great, still very flexible.

I did discover one missing bolt on the carburetor bowl, so that could explain why it looked look there was blow back out the front of the carb. Also, the hose on the fuel pump looked like it could be leaking a little bit too.
 
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