Diagnose my fuel issue please

Here we go. Over 1600 hours so we are getting into some more tempermental issue.

93 ski Nautique, PCM ford 351.

The boat will start up and run fine. Sometimes (emphasizing the sometimes) we will take the boat on plane and run it at higher RPM's for 20 minutes and then bring it back down and it won't idle it will just stall out.

The other issue (probably related but not guaranteed) when the boat runs fine sometimes we will power down and it will lose it's prime. Only way to get it started is to put a little gas in the carb and prime it. It will start up and run fine.

Fuel pump??? I took it off and replaced the gasket but didn't have a new pump to try.

I am going to put one on order for SKIDIM.com anyway cause as far as I'm aware it has never been changed so it's time. Any other ideas?

Yeah I have replaced the fuel filter. I talked to a friend who is a boat mechanic and he said it probably was NOT the pump.

I fill up off the road and have been for about 3 years now. He thinks the ethanol has caught up with me and it is really cleaning out the bottom of the tank and sending lots of bad things into the filter/carb.(I have never used an additive). He said to change the filter again add some fuel additive, play with the floats on the carb a bit to increase the fuel mixture and see where that takes me.

Any one had similiar problems with ethanol?

Carb has been rebuilt. Probably around 800-1000 hours. We're closing in on 1700 now so it is time. Planning on doing it at the end of this season. Hopefully I can get it running until then.