74 Evinrude 15 Problem

[pwiseman]

My fried has an OMC 15 HP. He just had it tuned up - new plugs, carb kit, impeller. He had it at my house two weeks ago and it ran great in the barrel. We went out for opener and had some problems. I noticed he was pumping the ball a lot before he started it and he said "it should get hard". I said you should try and start it after 4 0r 5 pumps, but it was too late at this point. The motor was flooded out and we did get it running a short time after drying out the plugs. Seems the plugs are getting fouled and there is too much gas going in. Wondering if he overpumped the ball and caused damage or if something might have jarred loose on the road.<br /><br />We did take the gas tank and it ran fine on another motor. I can say it is not the gas, the hose or the tank.

 

[Xcusme]

Re: 74 Evinrude 15 Problem

Paul, Since you've ruled out any issues with the fuel,tank and hoses, look again at the carb. Sounds like the carb float-needle is not sealing. If you still have the older type cork float, replace it with the newer plastic variety. Old cork floats can sink, allowing too much fuel into the carb body.

 

[pwiseman]

Re: 74 Evinrude 15 Problem

Originally posted by Xcusme:<br /> Paul, Since you've ruled out any issues with the fuel,tank and hoses, look again at the carb. Sounds like the carb float-needle is not sealing. If you still have the older type cork float, replace it with the newer plastic variety. Old cork floats can sink, allowing too much fuel into the carb body.

Float was replaced in the carb job. Could too much pressure on fuel hose cause a problem with the seal?

 

[Xcusme]

Re: 74 Evinrude 15 Problem

I wouldn't think so, but too much pressure is just that, too much. The main idea is to pump the bulb to push fuel past the fuel pump and then to the carb. When the carb bowl is full, the bulb will stiffen up. Continuing to pump the bulb serves no purpose, the flow of fuel into the carb should be stopped by the needle in it's seat. If there's trash holding the needle open or the needle-seat combo are not allowing a good seal, that's another matter. I would guess that the fuel pump's pressure is about 1.5-2.5 PSI for a diaphragm driven pump under normal running conditions. If the pressure in the fuel lines is increased, it should be relieved as the motor runs and the needle valve opens. After the fuel line pressure is normalized, it's the fuel pumps job to draw fuel from the tank by suction and supply fuel to the carb. All of this works well if there's no air leaks in the suction side of the fuel pump or hoses going to the carb. The tank vent has to be open, either manually or from a built-in air vent, otherwise, the pump will have a hard time drawing fuel from the tank.

 

[pwiseman]

Re: 74 Evinrude 15 Problem

Makes sense. Only thing I can't figure out is why it ran great two weeks ago and then it has this problem. It was like 45 degrees this weekend when we tried to run it, so that could be part of the problem - it was 75 two weeks ago. Sounds like something came loose on the trip to me. Looked to me like gas was running through, so you are probably right on the money with the valve not seating.