mecury outboat help

Robert Stanfield

Robert Stanfield

Active member
Ok I never was the best at technical names of stuff but am pretty handy getting most anything to work normally , But my buddy just bought a 1996 25 mercury outboard (newer then mine) and this thing has me baffled I am about ready to take a sledge hammer to it :)

serial number is 0G376909 the carb doesn't have the forward choke assembly as shown in parts diagram for this shown for this number

What I have done:
I rebuilt the carb (and have been back through several times just to double check)
has new fuel tank
has new fuel line
tried another buddys fuel tank and line (did the same thing)
tried another buddys whole carb! (still did the same thing!)

as fa as I am concrened I have ruled out the carb and the fuel lines and tank.

Motor starts right up , runs for 1-4 minutes then revs up and dies , it does not run as smooth as my motor but not as bad as I have heard others run either

anyone have any ideas?
 
I'm no expert so keep that in mind. As I read the post I wondered could you start it up right after? I had a similar problem, with a '91 Merc25hp, where it would run seemingly ok then die. Few squeezes on the ball, pull the cord and she went ok for a while longer. Found it wasn't the line, but the connector on the motor was broken. Seemed to be moving a bit and letting in enough air to cause issues. Replaced the connector there and haven't had a problem since.

Just a thought to look at.

~Dave
 
yes it will start right after it dies just pull choke out and one or two pulls to fire , I do squeeze the ball again just out of habit but the new one is about half pressure so I tried another buddys tank and line form another motor and that one stays hard but the motor still runs then revs up and dies out
 
If it will run on when you squeeze the ball just before it dies, you may have covered the vacuum port with the gasket for the carb against the motor. I did the same thing on mine. Three trips thru it and I found the small hole the new gasket was covering.

I dont remember if I had to flip it or if I needed to use another of the gaskets that came with the kit but it runs like a rocket and starts on the third pull every time or something is wrong.
 
Just out of curiosity....is it starting on all cylinders? What is that a 2 cylinder?

Seems like the choke is choking it out.
 
Bob,
I have the factory book for that motor.
If you want me to fax you some of the pages I can but it wont be today.
 
Sounds like the same problem I was having with my 20hp.
Will it continue to run if you keep squeezing the bulb?
 
Billy,
No it still dies if you do the ball or rev the throttle

Bob,
I don't have a fax is there any chance you could scan and email them to me? goldhunter_2@yahoo.com
 
I had a motor this year that was doing that. Carb was loose and sucking air underneath it. Run 2-3 minutes at idle. Give iut gas, it died. Maybe try looking for loose or broken hoses and fitting. Places it may be allowing air leaks in.
I dont know, I am no mechanic.
 
If it was OMC, I'd say the fuel pump needs to be replaced, or at least rebuilt. Not familiar w/25hp Mercs though - is there an accessible fuel pump on them?
 
Mike,
an air leak was one of my first thoughts I tighten down the carb good if its leaking I am 99.9% sure it isn't form behind the carb

Mark,
the fuel pump was rebuilt it is located on the side of the carb body
 
Geez, Bob, that's a tough one. Something is affecting the fuel flow, apparently. Hmmm...double check hoses for leaks - air leak somewhere is about the only other possibility?

Is the bulb empty after it dies? Do you have to pump the bulb to get pressure up again after it dies?

How about the interior fuel lines that run from the incoming fuel fitting to the carb? Replace and try - simple and cheap maintenance. May be a crack on the back of the incoming fuel fitting that's providing an air leak...

Scotch, for you now. Drink and think. Does it for me on occasion.
 
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Bob,
did you take the carb off and check for the vaccume hole and the gasket alignment?
All I saw in your post was a ref. to tightening the bolts.

I am still looking for a scanner.

May just be easier to photo copy a few pages and send them to you.
 
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