Fuel tank problem

[lanierseapro80]

I’m having issues with my gas tank. I believe it has trash or gunk build up (the gas in it maybe 5-10 years old, with exception of 15 gallons I mixed in with it). Marine Staybil and ring free we’re both in the tank prior to sitting. The motor runs fine under 2k rpm, go over that and the prime ball gets sucked in. I just tried a portable tank and I have no issues, it runs great wide open. I have read where to use the prime ball to drain all gas, but I need a way to get whatever trash is in it out. Any advise would be greatly appreciated.
Thanks

[gnrphil]

Anti siphon valve could be the problem and or the pick up tube getting clogged, best way to drain the tank is to remove the fuel sending unit and siphon or pump out from there.

[lanierseapro80]

Thank you very much for the information

[freezerfiller]

I'd bet money it's the antisiphon valve since it has been sitting.