1985 merc 260, I installed a rebuilt carb and changed fuel water sep last night. I ran the engine today, ran smooth for about 10 min then it puked, I saw black oil in the exhaust and was subsequently running very rough and couldn't run at idle any more. any thoughts. Man I am ready to give up with this motor.Thx

Jim

Sounds like you may have gotten some dirt caught in the needle and seat causing a flooding condition. Try pinching off the rubber fuel line and running the carb dry. Then release it and restart it. Sometimes this is enough to flush it thru.

Thanks Mo I'll give it a try tomorrow. The motor was running real smooth for about 10 mins. The motor also has about 40 hours on a rebuilt though the engine hasn't been run supposedly in about 10 years. I have been running it on the hose for several weeks now trying to work the kinks out.



And just for clarification are you referring to the return line that goes from the carb back to the fuel pump? The main fuel line is not pinchable. Thx

What if I were to shut the fuel valve off, run the carb dry, then open the fuel line, and just crank it without starting to get fuel back in the carb. ?

Ran the motor again, I shut the fuel line valve, the motor was running very nice and smooth. I turn the fuel line valve on and it floods the engine immediately. I shut the fuel line valve again runs smooth until carb runs dry. ??

I guess what I am saying is could it be the fuel pump? OR am I still looking in the carb(it was rebuilt on monday) and ran well for about 10 mins today then puked.

Your needle and seats not working.

Take the carb back off.


jt

Is it a mechanical or electric pump? If mechanical you can just look at the pump and see if there is fuel in the clear line that goes up to the carb. If there is you have a bad pump.

You could be over preasureizing the seat and causing the issue. When I put new high volume pumps on my boat I had the same problem. So I put a regulator on it. You will need to check the preasure going into the engine to be sure.

However if all that you did was to rebuild the carbs then I am guessing that you have a stuck needle. Take it apart and rebuild it and you should be fine.

Jon

OK, Thanks guys, off it comes and back to the guy who rebuilt it. There is no fuel in the fuel return line. thx again
Jim