Fuel leak 50 H.P. Yamaha 4 stroke

[Makky]

I have a peculiar fuel leak on my 2000 50 h.p. yamaha. I noticed a serious gas spill on my garage floor. Taking off the cover I could see gas visibly dripping from the bottom of the carb section. I disconnected the gas line and cleaned up the spill. When I tilted the motor about a cup of gas spilled from the inside of the case. I cleaned everything bone dry and I again connected the gas line and pumped the bulb to pressurize and I experieced the same serious leaking of gas. So I cleaned it up again and came back to it the next day. I connected the fuel line again. Now here is the strange part, it now will not leak. I can pressurize the carbs by pumping the bulb and everything is normal. One other thing that may or may not have anything to do with it. I am using my old Johnson fuel tank. That tank does not have a vent screw. The Yamaha came with a tank that had a vent screw. Any ideas will be greatly appreciated.<br /><br />Makky

 

[45_red]

Re: Fuel leak 50 H.P. Yamaha 4 stroke

I wouldn't use an unvented tank, it can build up a lot of pressure as temperature rises and pull a lot of vacuum as the temperature drops and when you are drawing fuel.

 

[radsrh]

Re: Fuel leak 50 H.P. Yamaha 4 stroke

Sounds to me like a float was stuck in the down position and the needle was open and let the gas overflow. For some reason it must have gotten unstuck when the motor sat over night, or the force of the fuel going in the bowls knocked it loose and it is working now. Also I would not use the unvented tank for the reasons that 45_red listed, on a hot day you could have a big mess from the pressure in the tank pushing on the carbs. I had a 10HP rude 4 stroke that ended up with flooded cylinders and a oil sump full of gas from a defective tank that did not vent on a hot summer day. And when running WOT you could cause a vacuum and stall condition.

 

[Makky]

Re: Fuel leak 50 H.P. Yamaha 4 stroke

Thanks guys. That certaintly explains my problem. I took it out on the water yesterday and it works great. Exterior of the carbs are all dry. So I will have to vent that tank in the future.<br />Thanks again for the help it is greatly appreciated.<br />Makky