What is the best repair manual for a 1981 mercury 25 hp

[Kawaiikeno]

I have a 1981 mercury 25hp electric start motor that I've been working on that runs great at idle and mid range but has no top end at all.
I have gone through the carb and fuel pump replaced the gaskets and cleaned it, it has 125 psi compression I noticed it has replaceable main jets but I can't locate it and the parts break down doesn't show where it is located.
thanks Mike

 

[flyingscott]

Need your serial # and factory manual is always the best.

 

[Kawaiikeno]

Mercury 25hp serial # 5786979
Thanks Mike

 

[flyingscott]

The main jet is in the float bowl just unscrew it. They do not need to be replaced just cleaned. #19 in the parts diagram. Did you assemble the fuel pump correctly? Is the base gasket on correctly?

 

[Kawaiikeno]

I will go through the carburetor again and verify everything.This time I will clean the fuel filter again and replace all the lines I looked at the filter and it looked good.
The problem started while making a 5 mile run to shore after fishing it just started dropping power when it got down to 1/2 throttle it seemed ok. the plugs looked good and the compression was 125 on the top and around 123 on the bottom two trips before the impeller and switch box (CDI) were changed.
I have 4 Evinrudes I've redone but this is my first Mercury besides it has electric start.
Thanks Mike

 

[Kawaiikeno]

I tore the carburetor back apart and checked everything out the carb is a BC1A .
There is no #32 in the exploded view (a jet) there is a threaded hole opposite the slow needle with nothing in it.
It still idles good and has good part throttle but dies above 1/2-3/4 throttle.
Does anyone know what the micro switch does
Thanks Mike

 

[The Force power]

It still idles good and has good part throttle but dies above 1/2-3/4 throttle.
Does anyone know what the micro switch does
Thanks Mike

The "micro switch" is most likely the manual push button for the "fuel enrichment valve"
It is possible that the valve is stuck open & it's allowing fuel from the carb-bowl to flow into the intake & flooding the engine.

Pinch-off the small hose and run it above idle for a few seconds & then full speed to see if it runs properly.
Another way of checking.... pull the hose off the valve (that is between the valve and the intake) Run the engine and see if fuel is coming out of the valve

 

[Kawaiikeno]

I figured out the micro switch it's a neutral safety switch.
I noticed it doesn't always keep the fuel filter full it fills it up then lets it run down about 3/4 then fills it up again I'm going to bypass the filter and keep pressure on the pump and see if that helps.
Thanks Mike

 

[The Force power]

I figured out the micro switch it's a neutral safety switch.
I noticed it doesn't always keep the fuel filter full it fills it up then lets it run down about 3/4 then fills it up again I'm going to bypass the filter and keep pressure on the pump and see if that helps.
Thanks Mike

How are you going to keep pressure on the pump?
The pump keeps fuel supplied to the Carburetor and by the sounds of it; it's not.
Inspect all your fuel-lines / connectors & vent in tank

 

[Kawaiikeno]

I'm going to start a new thread that's more inline with my problem of no full throttle.
Thanks Mike