Jaka - The reason is this: The idle needle must be opened too far to compensate for having to pull the fuel so far. On the test stand, the tank was directly below the engine. On the boat, the engine is (carb specifically) is 2" farther forward from the tank. The last time I ran the boat, I got the mixture dialed in to where I wanted it, but it would not stay running without glow attached. I had to make an adjustment on the angle of the engine which lifted the carb a bit higher than originally also. When its all said and done, the centerline of tank is 6.5" below the carb and 2" behind. Considering the engine must pull fuel from the back of the tank (which is another 2 1/2 inches away), I think realistically this is the best way to eliminate fuel delivery problems from the equation. The engine ran fine on the stand, but we all know once the engine goes into a plane (or in my case a boat) there are other variables effecting the performance (or lack of) of the engine.

I used a tach to set the needles. If I kept it WOT, it would stay running fine but back down to idle or mid-throttle it would up and quit. Glow plug soaked with fuel. I cleared the crankcase and cylinder several times. I tried leaning the idle needle down more, but that created a lean transition and very high idle. I'm trying to go with the lesser of two evils by using the pump.

Thanks for the tip. I might try that.