2003 Volvo penta 3.0 stops running

[Bigbird2003]

I have a 2003 caravelle with the Volvo penta 3.0 (holey carb). The boat runs good about 90% of the time but the big problem is when I load it. I run up on the trailer and the motor will run fine till I pull it back to neutral and it dies. After it dies it will not start back and sort of smells flooded. I've tried to make it do the same thing in open water and no luck. Only place it dies is on the ramp. I've changed my fuel separator, spark plugs, and used some sea foam. Can anyone give me any advise that will help. Thanks