9.9 johnson runs great for 5 minutes, then dies

[JKTrevecca]

I'm trying to help a buddy with his motor. He brought it to me saying it would run great for 5 minutes before dying (which I confirmed). I cleaned/re-built the carb, re-built the fuel pump, replaced the plugs, replaced the water pump, and then test ran it on a stand in gear with muffs on for about 15-20 minutes at cruising RPM's. It ran great and never died so I gave it back to him. First time out on the water, it died after 5 minutes again.

Any suggestions? I believe this is a 87 model "sailmaster" 9.9 tiller.

Thanks

 

[Crosbyman]

Re: 9.9 johnson runs great for 5 minutes, then dies

vent open ??

 

[Watermann]

Re: 9.9 johnson runs great for 5 minutes, then dies

Sounds like a fuel starvation problem to me. Bad fuel line he's using or like said above... he tightens down the vent. I would get the motor back the way he left it and see if there's fuel in the carb.

 

[OptsyEagle]

Re: 9.9 johnson runs great for 5 minutes, then dies

Tell him to try it again with the gas tank's cap off. Tell him to also keep his hand on the primer bulb and if it does it again, prime the bulb quickly and see if it revives. If it doesn't do it again, it is probably the venting, but the easiest way to determine is to run it again with the gas cap back on to see if it dies. If the priming revives it and the gas tank was open, it is either the fuel hose, the fuel pump, the carburetor inlet valve or an air leak somewhere. Since you didn't have a problem, I am guessing the tank vent, fuel hose or an air leak, perhaps at the hose connections. He might have the hose tangle around something in the boat or some other type of issue. I had a primer hose that acted up that way when the hot sun warmed it up. In the mornings it worked just fine and and would run for hours, however, in the afternoon, I got maybe 2 minutes from the dock before she died. I think it was the check valves in the hose, but I just got a new hose and never had a problem again.