Running/idling issues 2004 25hp merc outboard

[rattlenbang]

Hi all, I got this 13' Boston whaler as a tender for a motoryacht I just bought, and it came with this mercury 2 stroke 25hp outboard. The first thing with it was leaking fuel from the priming pump, so I replaced the primer pump diaphragm, as well as the fuel pump diaphragm. I also tore it all down and blew out all the ports and orifices. But it's still hard to start, and while most of the time it idles fine once warmed up, after a few minutes it'll eventually stall unless you pump the primer, and most of the time when you crack the throttle it seems starved for fuel and will stall unless you rapidly pump the primer or squeeze like hell on the fuel tank primer bulb. A lot of backfiring. If you can manage to get it past the throttle opening bit, you can get it wind right up and run like a top. But letting go of the throttle after a good run will result in a stall. I've checked that fuel is getting into the filter screen bowl, and into the carb input. I've cleaned the float bowl needle valve and seat. The gas is old but not rotten or stinky (the boat came with a couple of tanks, both filled with fuel) and I plan on replacing the plugs but haven't done so yet. Not sure where to go from here.

 

[indybleck]

Try some startron in the fuel, but fresh fuel will be a better idea

 

[rattlenbang]

Turns out the new gasket I put on had the hole misaligned to the crankcase. It was like 1/4" off. I cut it out into a slot put it all back together and now it keeps the fuel bowl full. What a PITA. The only thing remaining is that it doesn't idle well unless I pump the primer or I hold closed the enrichment solenoid on the top of the carb.

 

[Mohawkmtrs]

I see a complete carburetor cleaning in your future.