Stalling 25hp Merc May 2011

[Copper116]

I have a 97 Merc 25 hp outboard... I just bought it from a friend. It's been stored with StaBil for 2 years. I had to rebuild the carb because it wouldn't start.. it was gummed up. I rebuilt the fuel pump too just in case.
It started right up after the rebuilds. I noticed that when it did start, the fuel level in the filter continually dropped. I was told to replace the motor end of the fuel line due to the o-rings possibly going bad. That seemed to help... it only dropped slightly then. It ran good at an idle with the water muff connected.
A trip on the water resulted in a loss of power at higher speeds then it would often stall. Sometimes feathering the throttle helped but sometimes it wouldn't. The fuel tank vent was open fully. I haven't pulled the motor cover yet. Any ideas why it would stall? It starts right back up every time... it's just at higher speeds!

 

[Maxz695]

Re: Stalling 25hp Merc May 2011

definitly sounds like lack of fuel pressure. I would check the rest of the hoses back to the tank. may have a crack and sucking in just enough air to prevent a steady flow at higher RPMs

 

[Copper116]

Re: Stalling 25hp Merc May 2011

Sorry for delay... Well, I replaced the fuel tank because the pickup assembly was pretty well corroded beyond repair. I found a very thick oily substance in the tank so I filtered it before pouring it into the new tank. I flushed out the hose and primer bulb, finding more gunk in that too. I flushed the carb and it still would not start and or run without choking it constantly.
After the marine shops quoted me an outrageous price to just check it.. I tore it apart again. I ran fine wires and sewing needles through every orifice I could find. Sprayed out everything with carb cleaner and blew it out with an air gun. This time, after a little cranking, it fired up but a bit rough. I tweeked the idle adjustment screw and it's now running. It's still idling a bit rough ( my opinion ) but I'll run it a bit and see if it clears up and runs smoother. It may be only a typical 2 cycle behavior. Thanks.