I am running a 1987 Yamaha ProV150 on a 1987 Chris Craft Scorpion 168 Outboard bowrider. Issue at about 4300 rpm engine slows as if it has run out of gas and is starved for fuel. Things I have done: drained all fuel from below deck fuel tank and replaced with fresh fuel and added Seafoam, replaced the fuel pumps, gas supply hose from the below deck fuel tank to engine (including Primer Bulb and Engine Connector). Still have the problem. When I run on a Portable Tank I have no issues engine runs perfectly. Assuming the withdraw line may be blocked/clogged inside the tank I tried to blow compressed air directly into the withdraw hose (primer bulb removed) to the tank. There must be a check valve as the air just blows back. The Deck access cover has not been centred properly to pull the Sender for inspection. Short of cutting the floor, removing and replacing the tank. Does anyone have any thoughts? Despite being 28 years old the Boat and Engine are in pristine condition.
