I have a 5.7L Marine Power engine in my 2006 Tige 24VE. I can run at 10-12 mph with no problem. When the engine has been off for several hours, I can throttle up to towing speeds (30+ mph). After 2-3 minutes, the engine power drops, surges back partway, drops again, and will continue winding down until the engine dies (or I drop it to idle speed). Even though the tank is nearly full, it's the same experience as a vehicle running out of gas. I can continue at low speeds again but can't throttle up without the problem repeating. Any suggestions on how to isolate and repair this issue? thx