Please Help

[glastron1]

I have a 1998 glastron with a 4.3l merc cruiser. The problem! Boat runs great at idle speed will go all day but when I try to increase speed boat comes all most to plane then the gas guage drops to empty and the boat starts to dye like it is geeting no fuel. I have changed all filters, rebuilt carb, new wires plugs,fuel pump, drained the gas tank completly. When I first changed the fuel pump ran great for about 15 minutes then back to the same old thing. I don't know if this has anything to do with it but some times when I fill the gas tank fuel will back up in the fill tube like ther is some kind of vapor lock. Some one please help

 

[MikDee]

Re: Please Help

Have you checked your fuel tank vent? If no air goes in, no gas comes out! Find it, see if you can blow into it, if not it's clogged clean it. (I know it's a primitive way, and don't taste good, but it's an effective test method).

 

[wire2]

Re: Please Help

I think your gas gauge going to 0 is an indication of an electrical problem. Coming up on plane will cause the fuel in the tank to flow to the back, so there may be some fluctuation on the gauge but not to 0, especially if the tank is full.
I'd clip alligator leads on your + terminal of the coil and engine ground, then have a passenger watch a voltmeter when you accelerate. I believe you're losing the spark for some reason related to motion.

I saw a similar problem once in a friend's boat. I wanted to monitor fuel pressure from the pump, so I undid the steel tube fitting and added a brass "T", then connected 10' of urethane tube, with a pressure gauge at the helm.
When I was done testing, I removed the T and put it back to original. With fuel approved sealant.

 

[bruceb58]

Re: Please Help

Just as a test to see if it is a tank venting problem, try running without your gas cap. If that solves your problem, investigate your tank vent.

 

[wire2]

Re: Please Help

One other thought, (although it doesn't answer the gauge to 0 issue); If the fuel level in the carb bowl is low, tilting it during acceleration might starve the jets.
I know you rebuilt the carb, but could be as simple as stuck float valve.