2003 200 HPDI needs help troubleshooting -please help

[Grasscutter]

My motor sometimes has an alarm at low RPM's. I don't have the tach that tells me any info. There's plenty of oil and the motor is cool to touch. Is there a tool I can get to plug into the motor and diagnos the problem? What other reasons could there be for the alarm?

[boats.net]

If the alarm only goes off when it's in neutal then it's water in fuel alarm, check fuel filter. Otherwise probably need to replace water pump.