81 Evinrude 25HP Carburetor Question

[cchildr84]

I recently rebuilt the carburetor on my 81 25HP Evinrude, which i've done before with no issue, but for some reason this time couldn't get it to idle down. I think the problem is likely that one of the welch plugs wasn't properly punched in and it's sucking air. So I'll have to rebuild it again.

However, I needed to get on the water the next day, so I happen to have had a carburetor from at 35HP. Got it on, and it idled fine and passed all the in the driveway in a garbage can with water tests. However, once I got it on the water, it ran fine at full throttle, but I could tell it was not reaching the proper RPM and would only get me to 24mph rather than my typical 27mph with the 25HP carburetor.

My assumption as to why this is occurring, but please correct me if I am wrong, is that the jets are bigger and it's getting to much fuel. My question and the purpose of this post is, can I adjust the 35hp carburetor in some way as to restrict the fuel in order to get it to run at full throttle as it should until I can get the 25hp carburetor rebuilt properly and put back on?

 

[saltchuckmatt]

It should work fine with that HP range...did you perform the link and sync correctly? Is the butterfly completely flat or horizontal at wide open throttle?

If so your main jet could be the issue.

 

[saltchuckmatt]

In conclusion, you probably need more fuel not less on the high side.

 

[Crosbyman]

if you feel the top idle channel welch plug is sucking air a dab of clear nail polish or float airplane dope should stop any air leaks .

check for a clean feed route to the top drip chamber

 

[cchildr84]

It should work fine with that HP range...did you perform the link and sync correctly? Is the butterfly completely flat or horizontal at wide open throttle?

If so your main jet could be the issue.

I can take the airbox off and see. But to answer the question, all the linkages lined up the same, so no I, did not adjust any of the linkages.

 

[cchildr84]

if you feel the top idle channel welch plug is sucking air a dab of clear nail polish or float airplane dope should stop any air leaks .

check for a clean feed route to the top drip chamber

I think it's the one that is inside the bowl. As the top was good. The other on on the outside was leaking, but I put some jb weld on that one as that is all I had at the time.

 

[saltchuckmatt]

I can take the airbox off and see. But to answer the question, all the linkages lined up the same, so no I, did not adjust any of the linkages.

L & C is a must. Remove the cowling, put it on the lake and go to wot....push down on the carb linkage and see if it surges.

Eyeballing the butterfly is easier though and is part of the l&c procedure.

 

[airshot]

Never expect peak performance when cutting corners......

 

[cchildr84]

I had a thought last night. If I perform the link & sink and switch out the high speed jets would that do the trick?

 

[Crosbyman]

i would not play with design intent... best to fix the problem.

 

[saltchuckmatt]

I had a thought last night. If I perform the link & sink and switch out the high speed jets would that do the trick?

To repeat myself, the 25, 30, 35 carb is a direct swap (no porting, jet or intake issues) except I'm not quite sure of the year swap.

That's not true in other HP ranges.

Very simple task, while the motor is off...stare down the throat of the carb and see if the butter fly valve is completely horizontal at wide open throttle.

If it's not, then do the link and sync.

Many many many l&c examples online.

Best to learn this.