mercury 115 2+2 carburetor problem

[flasher]

i have a mercury 89 4 cyl mercury 115 hp ob motor that im having problems with a carburetor.the engine has the top 2 carburetors that are adjustable.the first carburetor the idle screw functions like it should.any adjustments that are made on the idle screw immediately are felt on the engine.i have rebuild the second carburetor twice to include a new float.the problem that im having is that im unable to adjust the idle screw.the manual says to start with 1 1/4 turns.i can open the idle screw as many turns and it will not flood the engine,at the same time if i close the screw it has not effect until the screw is about 1/8 from close before the engine dies.the engine will idle,but its getting too much fuel on that one carburetor and is causing the engine to pop every so often causing it to die at idle.any help will be appreciated.

 

[murraymtn]

Re: mercury 115 2+2 carburetor problem

Unfortunatly I have the same engine as you. But anyway here is how I
got mine to run. The idle screws are useless. Set them at about 1 turn out
and forget them. Get a small screwdriver about 6 inches long. Remove
you plug in the bowl that drains the carb. With the screwdriver there
is a jet straight back from the plug, reach in there and turn this jet out
3/4 of a turn. Do this for the top 2 carbs. Your engine will run like
a champ.

 

[flasher]

Re: mercury 115 2+2 carburetor problem

thanks for the reply,ill try that this weekend.

 

[sschefer]

Re: mercury 115 2+2 carburetor problem

Unfortunatly I have the same engine as you. But anyway here is how I
got mine to run. The idle screws are useless. Set them at about 1 turn out
and forget them. Get a small screwdriver about 6 inches long. Remove
you plug in the bowl that drains the carb. With the screwdriver there
is a jet straight back from the plug, reach in there and turn this jet out
3/4 of a turn. Do this for the top 2 carbs. Your engine will run like
a champ.

That's a very creative solution.

I'd like to see what happens if you disconnect the choke solenoid fuel line and plug it. The symptom described is typical of a leaky choke solenoid because it gets it's fuel supply from #1 and gives it to the other carbs. #1 will adjust fine and 3 and 4 don't adjust so 2 is always going to be where you discover the problem.

 

[Faztbullet]

Re: mercury 115 2+2 carburetor problem

With the screwdriver there
is a jet straight back from the plug, reach in there and turn this jet out
3/4 of a turn. Do this for the top 2 carbs. Your engine will run like
a champ.

This is a fixed jet and turning it has no effect on fuel flow!

 

[flasher]

Re: mercury 115 2+2 carburetor problem

well this past weekend i tried both suggestions.first i adjusted the jets,it had no effect.second,i disconnected and plug the lines that go to the fuel enrichner with negative results.the engine has a smooth idle if is ran on one cylinder.when both cylinders are running the idle loops and pops,as soon as you disconnect one of the cylinders the idle smooths out.

 

[flasher]

Re: mercury 115 2+2 carburetor problem

the problem has been corrected,it was the inlet needle valve that was not seating in the second carburetor.thanks to all that replied.