1995 proline center console sportsman, fuel leak

I recently purchased a 95 proline center console, I knew it had a small fuel leak when I bought it but I didnt know what I was getting into, what i thought was gonna be something minor has turned into something major. The boat has been at several shops and no one can find the leak. one guy said it was the fuel tank and would could nearly $4000 to repair. The boat does not leak out of the water . I have put a smoke machine on the tank, disconnected all fuel lines and pressured up the tank.. no drop in pressure, no fuel coming from anywhere, and no smoke. I took the boat out yesterday for the first time, and it starts to trickle gas into the bilge only when on plane, or almost on plain, then its a steady flow of gas, not alot, but enough that you can smell it all over the boat, and you can see the water beading up in the bilge area from the gas. Anyone had this problem before? or can anyone tell me a different method of checking it? Im an automotive mechanic, so I have some diagnostic experience, just not on a boat lol, thanks in advance

Re: 1995 proline center console sportsman, fuel leak

I think I'd work from the engine connections back. You could run a fuel line directly from the tank to the engine, by-passing the water seperator, bulb, etc and see if that makes a difference; it could be a connection along the line. If not, then it's at the tank.

Does it do this regardless of how full the tank is? Can you remove the deck plates and observe the tank and fittings? Put a paper towel around the pick-up and guage sending unit connections. Check your connections for the fill and vent tubes.

The fact that it does it on a plane suggests to me that something is occuring from the pressure of the gas in the tank pushing to the rear of the tank. i suspect the smoke test didn't get the pressure built up but you would know. Also it only takes a tiny bit of gasoline to smell it so maybe the smoke wasn't apparent.

Not sure why it would be $4000 to remove and replace, but I've seen boats where the tanks had to be busted up to get them out, then replaced with a smaller one. Or do they have to remove the whole cap?

Re: 1995 proline center console sportsman, fuel leak

I disconnected all lines from the tank and pressured it up with smoke. I heard the tank pop from the pressure..held pressure for 25 mins. no smoke or gas anywhere.. assuming the pressure would push gas out if the leak was on the bottom and smoke if the hole was above the fuel level.

there are only 2 inspection plates on the floor, small round plates, one above inlet and one above the outlet. Cant see much of the tank, but if you stick your head down in the bilge and look forward, you can see the whole top of the tank, and no smoke is apparent.. I pressured up each hose individually and found no leak anywhere.. also the hoses were changed before i purchased the boat , trying to fix the leak..

I have checked every clamp, every hose, every inch of the tank that i can see.. could the over flow vent create a suction or something that would spill into the boat? I cant see how, but im new to boats.