I am looking for some help with my 2001 mercury 150 Optimax. The motor is giving me problems that no one seems can give me a straight answer. So,here it is... To start the motor, I would have to give it gas or full throttle. When I put it back in a neutral position, the engine died off. If I go to put it in gear quickly the motor will run fine as long as its under 2000rpm and when I put it back in neutral again, it would died off. I can't get the motor to go past 3200 RPM, no warning sound, engine does not over heat, water shoot out strong. After about two days the motor would started fine and ran fine ( maxed out RPM) once the motor stop for about two hours or so, the problem came right back again. This would go on and on. I have replaced many parts such as, Spark plugs and wires, new fuel lines, fuel filter, poppet valve, water pump,etc. I've paid to have the motor hooked up to the diagnostic computer at the dealership and still nothing. My love for boating is the reason why I am not going to quit until I have my boat running fine again. However, I am running low on cash and can't just pay for parts here and there like fuel pump, injectors, etc as those parts are not cheap just to troubleshoot. ( Recommended by mechanic). Thank you in advance.

If your mechanic has changed all these parts and hasn't come close to finding your problem move your boat to another dealership.
A qualified Mercury technician should be able to pinpoint the problem and not just throw parts and your dollars at it until it accidentally runs.
If he can't verify your fuel/air pressures and verify whether or not your injector/s are having problems RUN AWAY!!!

Hi. if your mechanic did not change, check the crank position sensor (CPS) resistance with the multimeter (300-350 ohms), sometimes the DDT or CDS don´t do the right reading. Bad rpm readings are a sign of a bad cps.

hope it helps.