Fuel comes out of exhaust

[crookedmullet]

I've got a 2001 Mercury 90hp-3 cylinder on a very nice 17' Action-craft that was donated to our company. When I picked it up a month ago it ran very nice and very fast. Last week I received a maint. form saying that it was running rough. I checked it out and found out it would only start with the throttle opened all the way and it was sputtering really bad. When you bring it back to neutral slowly, the engine dies. Even with the throttle opened a 1/4 of the way, it's like it's not getting enough fuel.<br /><br />So I do a complete carb rebuild, replace all the fuel lines, filters and primer, check gas tank vent, replaced the diaphrams in the fuel pump(which I found a crack in 1 gasket and a pin-hole in the diaphram), checked timing which was good, I've got spark in all the plugs and finally, I'm not losing any electrical anywhere. So, happy with finding a problem and eliminating any other possibilities, I trailer it too the ramp, and start engine. Same thing happens, it won't start in neutral, have to have throttle open at least half way, but the sputtering was eliminated. Bring the boat back to the shop and as I pumped the primer bulb I notice fuel coming out of the exhaust by the prop. This is where I'm stumped...why is fuel coming out of the exhaust even after I rebuilt the carbs again and made sure floats were seated right?

 

[Silvertip]

Re: Fuel comes out of exhaust

It's getting too much fuel if its running out the exhaust. Since the fuel pump operates on vacuum pulses off the crankcase, your fuel pump rebuild may have been done incorrectly and fuel is being squirted right into the crankcase as you squeeze the bulb. The engine can also suck it straight in creating the very rich condition.

 

[crookedmullet]

Re: Fuel comes out of exhaust

Well, the fuel pump it was. Quicksilver had put the wrong diaphragm in their kit. Had to use the old one, which just happened to be good. Engine fired right up.