Gas pick up problem

[highpond]

I have a question about gas pick up. When I run my motor for a while then stop at anchor to go swimming or have lunch , the motor will be shut off for an hour or two. When it's time to crank it up and get going I can go about 3 to 4  hundred yards and the motor will shut down, like it has used up the gas reserve in the water separator and the carb. bowels, The motor acts like it had run out of gas. I then have to prime the bulb to get gas back into the system and the motor will start and continue to run. The question is, is it possible that there is a vacuum created in the tank as gas is drawn out that is pulling the gas back when the motor is shut down? I have changed the check valve at the tank. Replaced the bulb. Tightened all the clamps. All gas seems to be drawn back from bottom of the bulb back. Yes I've checked to see that the check valve is in the proper position to not allow the gas to syphon back which leads me to believe that it could be some type of vacuum in the tank that has developed. Maybe air not getting through the overflow.

Anyone have a solution?

 

[kaydano]

Open the fill cap? You'd definitely know there was no vacuum then...

 

[spinzone]

Really sounds like the negative pressure of vapor lock. The black cowl of a Mercury creates an oven in the summer heat. I used to have a similar problem on a bass boat I owned. Only my boat wouldn't start for an hour or so after I shut it off. The hot gases under the cowling will push fuel away from the carb bowl until it cools enough to return to liquid form.

If Dano's trick doesn't work, I'd suggest making sure you open your cowling when you anchor to allow the heat to escape. I'd bet you that you find this quickly solves your issue.

Oh, and ethanol in fuel these days compounds to the vapor lock issue.

 

[hapehour]

Check the fuel line from the tank to the motor,  if it`s dry rotted or cracked it sucks air an causes that very problem. It`s worth a shot, you have to eliminate the potential problems..