15 hp four stroke stalls

[BAA]

I have a 1999 15 hp Merc that I use as a kicker motor for trolling. It will run good for a few an hour then stall the primer bulb is soft. I pump the bulb back up and it will start and run for just a few minutes long enough to use the fuel that was pumped into it I can pump the bulb and it will stay running. It is hooked up to a built in fuel tank with its own pickup. I have replaced the bulb twice had all the fuel lines replaced from the tank to the motor and all the fuel lines inside the motor with a new inline filter mercury brand. The fuel pump is new from mercury and the carburetor has been rebuilt twice by two different mechanics. I also took the fuel line and put a tee in the line for my main motor (which runs fine) and tried that and the same problem. Pulled the floor up to get to the fuel tank pulled out the dip tube and the screen was not plugged. Pressure tested the fuel system and had no leaks. Also put a new water impeller in. I don't know where to turn next anybody have any other suggestions

 

[MH Hawker]

Re: 15 hp four stroke stalls

It sounds like its sucking air some place.

 

[BAA]

Re: 15 hp four stroke stalls

It sounds like its sucking air some place.

Fuel system pressure tested it will run all day if I put the motor in a tank using the same fuel lines I leave it on the boat and just put a barrel under it

 

[MH Hawker]

Re: 15 hp four stroke stalls

Its not under a load on muff or a tank.

 

[BAA]

Re: 15 hp four stroke stalls

Its not under a load on muff or a tank.

When I put it in the barrel I put the motor in forward gear at idol is that enough load? It is very frustrating trying to figure this out when it runs it runs great had it to a few mechanics and they can't find a problem changed about everything next is the thermostat

 

[racerone]

Re: 15 hp four stroke stalls

Is fuel left in the carburetor when motor is not being used ?---------The passage ways / jets in these carburetors are very small and plug up easily when fuel sits in the carburetor.-------Try a thorough cleaning of the carburetor.---------Then again just opening the low speed mixture screw may be all that is needed.

 

[MH Hawker]

Re: 15 hp four stroke stalls

Is fuel left in the carburetor when motor is not being used ?---------The passage ways / jets in these carburetors are very small and plug up easily when fuel sits in the carburetor.-------Try a thorough cleaning of the carburetor.---------Then again just opening the low speed mixture screw may be all that is needed.

I am sure i am wrong but i thought the newer 15 and less dont have a adjustable mixture screw unless merc got about to fixing that.

 

[ondarvr]

Re: 15 hp four stroke stalls

I am sure i am wrong but i thought the newer 15 and less dont have a adjustable mixture screw unless merc got about to fixing that.

By law the adjustment screw is set at the factory and sealed, it is set very lean, on many possibly too
Lean. The dealer can't adjust it either, they can clean the carb or replace it, but not adjust it.

Most owners drill or pry out the seal and adjust the screw, it will frequently run much better afterwords.

 

[ondarvr]

Re: 15 hp four stroke stalls

The squeeze ball won't be hard after it has been running, but it shouldn't be empty, the arrow on it should be pointing up also.

The symptoms sound like an air leak, check the O rings in the connectors, they frequently check out as good under pressure but fail under vacuum.

 

[MH Hawker]

Re: 15 hp four stroke stalls

By law the adjustment screw is set at the factory and sealed, it is set very lean, on many possibly too
Lean. The dealer can't adjust it either, they can clean the carb or replace it, but not adjust it.

Most owners drill or pry out the seal and adjust the screw, it will frequently run much better afterwords.

Yea thats what I was thinking.