"It's a good idea to run a
"It's a good idea to run an alternate fuel system in a situation like this, and you've already done that with all the new stuff. Is the fuel bulb new?
Here are some other "alternate fueling" ideas to confirm that you are or are not feeding the engine well with fuel:
- If you suspect air in the fuel and fuel starvation due to air being fed to the carburetor, find a little piece of tubing as a union fitting and install a short section of clear hose at the carburetor inlet (gasoline compatible, and if not, don't use it for long), and watch what happens when you increase power.
- You could install a vacuum gauge in the line between the tank and the carb, to see if you have some major restriction. You can also remove the hose from the engine fuel pump inlet and see how your hand bulb pumps fuel.
- You could run a hose straight from the fill cap opening into the fuel tank to the inlet of the engine fuel pump, and see if it changes the way the engine works. If not, you might be looking at a carb that can't keep up with demand due to the bowl level getting too low at high power settings.
- If the carb intake is accessible during boat operation at high power, you could give a short one-quarter second ether blast into the intake as soon as it starts stumbling and see if the engine recovers momentarily. Don't give a continuous blast or bad things can happen. Don't even attempt to play with trying to put gasoline into the intake under those conditions either. I had a friend get some 3rd degree burns and his clothes were burned off, threatening his life. Be careful.
- You can continuously squeeze the bulb when you expect the engine to start stumbling, and if it changes the symptom, then you might have some sort of fuel feed problem. I installed a 7 psi electric fuel pump between my bulb and the carb while troubleshooting a fuel starvation issue. The engine fuel pump pulls fuel right through it, so the electric pump can be there and not hinder operation while it is turned off. After I fixed my fuel starvation issue, I use the electric pump only for priming so I don't have to squeeze the bulb. The squeeze bulb will push fuel through the electric pump, and the engine diaphragm pump will pull fuel through both of them. Adding the electric pump did not change any operation characteristics. It can be a great troubleshooting asset. It is not mounted, it just exists on the fuel line.
- If you suspect a problem with ignition, wear a small AM radio with an ear plug tuned to a blank area of the AM band so you can hear the ignition noise. You'll get familiar with how it should sound. If the noise disappears during the stumble, maybe it's an ignition issue. If the noise just spools down as the engine spools down during the stumble, then the ignition may be okay.
- Timing problems shouldn't kill the engine, but I suppose it's possible. Does it die and totally stop running? Or does it just stumble out but keeps running?
Lastly, if the fuel is getting to the carb without air in it and it's not restricted in any way, then if it's fuel starvation issue, it has to be in the float valve or the float could be sticking somehow, or something is in the carb inlet fitting hole. I always test carb float valves by removing the bowl, and letting the float hang down all the way to open the float valve all the way. You can pump fuel through it with the bulb or a fuel pump, and it should flow pretty well through the valve. You should be able to lift the float and shut the fuel off completely without much force. Don't exert much pressure either way on the float so you don't bend the tabs. Above all, make absolutely sure that the float valve fixture, seat and carb inlet is completely clear of any type of debris. A piece of crap in this area can severely hamper the ability of the carb bowl level to stay where it's suppose to be under higher power settings. Also, make sure the float actually "floats".
Good luck
Bob"
