1990 yamaha 3hp runs a few minutes then cuts off.

[gaston9mm2]

It runs about 2-3 minutes then cuts off. When its running it runs really good. I have put on a new carburetor, water pump and thermostat and spark plug. It also has a new fuel pump. I have to choke it to get it to crank back up when it cuts off. Any other time it cranks first pull. I'm not sure what else to do to it. Any help would be greatly appreciated.

 

[mike_i]

what's the condition of the primer bulb when it dies, it's flat and compressed? When the motor starts to die can you pump the bulb, if so what happens? If you have a fuel filter have you checked it?

 

[gaston9mm2]

It's got a small attached gravity feed tank. I even clean and checked it to make sure it is venting. I also replaced the fuel lines. Once it cuts off if you pull the choke out it will crank right back up. Or if you let it set a bit it will crank without choking it.

 

[robert graham]

Maybe that carb float needle valve is sticking some and letting the float chamber get low fuel level....

 

[gaston9mm2]

Robert what would be the best way to tell? I have taken the carb off again and there is fuel in the bowl when I take the drain screw out. Can I tell by that?

 

[99yam40]

sounds like a restriction that will not let enough fuel to flow into the bowl while motor is running.
thus using more fuel than can be replenished.

does this carb have any type of pump to help transfer fuel?
a screen or filter in the tank/line?

 

[gaston9mm2]

Where the line runs into the carb is a square box like a pump but it's more just 2 diaphragm gaskets.

 

[robert graham]

Robert what would be the best way to tell? I have taken the carb off again and there is fuel in the bowl when I take the drain screw out. Can I tell by that?

I have a 3HP Tanaka outboard and if the motor was doing what yours is doing, and I was sure the gas tank was venting then I'd check/clean/replace that float needle valve....the needle may go into a rubber seat and be sticking closed under certain conditions....especially with a gravity feed fuel flow like mine....maybe yours is gravity flow with the built in fuel tank? Another restriction may be in the fuel petcock....I replaced mine with a black plastic unit from a chain saw...

 

[gaston9mm2]

Mine has the plastic gravity mounted tank on the top of motor. I was cleaning the pet cocktail and as I was reassembling it I noticed at the top of the fuel tank on the side there is about a 1in crack in the plastic. I'm wondering if this could be the problem letting to much air into the tank maybe? That's just a guess on my part.

 

[robert graham]

Could well be your problem....Northern Tool or similar store sells those little plastic petcocks and clear yellow fuel hose and maybe just replace that cracked unit.....

 

[99yam40]

tanks have vents to atmosphere so the fuel can drain out.
I do not see how a crack could let too much air into the tank when to tank is already vented

 

[gaston9mm2]

That doesn't appear to be the problem. Even took carb back off and cleaned it again. Still same issue.