having trouble getting a 71 johnson 60hp, 3 cylinder running correctly.

[jwilkey84]

I am trying to help out a guy, usually I just work on my own and am dangerous at that! He has a 71 johnson 60hp motor with 3 cylinders (3 carbs) and if he sprays a gas/sea foam mixture into the carbs it will start and run for 5-10 seconds, then dies. The fuel in the tank is new, the tank is new, compression is 135, 135, 130; so not bad. it apparently is getting spark because it will start. The fuel pump is pumping fuel. I took one of his carbs home tonight to clean tomorrow. The carbs all look clean on the outside, and the bowls are even fairly clean, but I want to look inside and see if there might be some gunk in the orfices. So i guess what I am asking is if I clean up all his carbs and still have problems, where should I look next? and how does the 3 carb setup work? I think the fuel is delivered to the center carb, then delivered to the top and bottom carbs from there. I unscrewed the drain screws on the bowls, and to my suprise fuel came out of the top one, but not the middle or bottom. With this setup, if the float is stuck in the middle carb, can fuel still be delivered to the other two carbs? I wonder if the floats are stuck in the middle and bottom bowls and preventing fuel from being delivered from the tank to the cyilnder. Thanks for the help in advance, you guys always come through for me.

 

[F_R]

Re: having trouble getting a 71 johnson 60hp, 3 cylinder running correctly.

There are three cylinders, three carburetors. Each cylinder is fed by it's own carburetor. Think of it as three single cylinder motors stacked on top of each other on a single shaft. So, if one carburetor has a clogged main jet, the cylinder that it is associated with won't get fuel. You indicated that two of them had no fuel in the bowl, so right there you know those two cylinders won't fire.

I think you are over complicating the fuel delivery to the three carburetors. A single fuel pump delivers fuel to a line that branches off in three directions. That "branch" occurs at the center one, but the fuel is free to go in all three directions from there.

 

[durban]

Re: having trouble getting a 71 johnson 60hp, 3 cylinder running correctly.

i would start at the source first , check the diaphragm in the fuel pump first

 

[eavega]

Re: having trouble getting a 71 johnson 60hp, 3 cylinder running correctly.

check the tee on the middle carb, and the fuel lines to the other two. If those fuel lines are old, it may be time to replace them with ethanol-resistant lines.

-Rgds

 

[jwilkey84]

Re: having trouble getting a 71 johnson 60hp, 3 cylinder running correctly.

well I assume the diaphram is good since when I crank the motor over it pumps fuel out of the line when I have it unhooked from the carbs. I did notice that the lean rich needle was only turned out about half a turn when I was cleaning the top carb today, shouldn't the be more like 1 1/2 turns out from being seated? If the other two carbs are similar, that could be a problem, right? running too lean?

 

[Daviet]

Re: having trouble getting a 71 johnson 60hp, 3 cylinder running correctly.

The static setting is 1 1/4 turn out from lightly seated, and fine tuned in the water with the engine in gear.
If the bottom two carbs did not have fuel in them, pull the carbs and clean them, paying attention to the tiny passages under the core plug on top of the carbs.
If you remove the bowel drain on the carbs and pump the primer bulb, fuel should come out off all three carb drains.

 

[boobie]

Re: having trouble getting a 71 johnson 60hp, 3 cylinder running correctly.

Pull the fuel lines going to the carbs that don't have fuel coming out of the bowls and pump the primer bulb. If you have fuel there you most likely have stuck needle and seats in the carbs.