Mercury outboard keeps stalling

[h2ocwilly]

I have a 1998 25hp outboard serial #0G727076 four stroke motor that keeps stalling while trolling. It seems to run fine while the RPM's are up. Its been in the shop a few times and they can't find anything wrong with it but we get it back on the and it stalls again while trolling. Is it possible that the priming bulb could be losing pressure and therefore running out of fuel? Is the priming bulb suppose to remain firm?

 

[oldman570]

Re: Mercury outboard keeps stalling

The priming bulb should stay fuel but not real hard as when you prime the motor as the fuel pump sucks the fuel from the tank after it has run for a shot time. If the fuel pump has not been rebuild lately , it could be getting a weak diaframe and not supplying enought fuel and pressure when the motor is idled for extended periods but will work when the motor is above a idle. If you squise the priming bulb when it wants to die at idle and the motor picks back up for a short time then I would check out the pump. Other wise you could have an air leak in the fuel supply system that would cause the trouble. The little O ring in the connectors might be the trouble. If it runs fine at the shop and they are using a diffrent hose an tank than what you use, then I would look into that first. JMO
Oldman570

 

[joed]

Re: Mercury outboard keeps stalling

Is it just stalling or is it coughing/backfiring and stalling. I had the coughing problem on 9.9 troller and the problem was carbon build up in the exhaust. They pulled the power head and chopped out the carbon deposits with a screw driver.

 

[h2ocwilly]

Re: Mercury outboard keeps stalling

Thanks for the input, I will check out everything you suggested. Btw they did use the same fuel line cause I took the boat in not just the motor.

 

[quicktach]

Re: Mercury outboard keeps stalling

How does it stall ...sputters or just quits ? Sounds like you are starving at low speed. Carb had a good cleaning and set up ? Tried a good decarbonizer (mechanic in a can ...from your Merc dealer) ? Could be low speed carb circuit. And don't forget plugs - are they clean?