I recently bought a 88' tracker marine boat with a 90 hp oil injected 3 cylinder on it. I was told the motor was last run a year or so ago, and ran fine then! The motor will idle fine in neutral and in forward and reverse gears, but when throttled up the motor dies. New gas was put in, in line fuel filter was changed, drained the float bowls on the carbs and I put a new diaphragm kit in the fuel pump. Little to no improvement was noticed after these steps. Any suggestions? The boat was owned by people I know, it has low hours and is in immaculate condition.