[sledstew]

I replaced the water impeller last week and that did not fix the problem. When the boat idles at lower rpm eventually the warning buzzer goes off, to get the buzzer to go off I have to drive the boat then it quits. I was wondering what it could be ,I'm leaning toward a bad thermostat on one of the powerheads,but why would it go off at low RPM and clear when you drive it at higher RPM. The owner of the boat said that the pressure gauge on the dash has failed (high) but that happened a couple years ago and it did not affect the warning buzzer.Also is there a pressure sensor for the cooling system on this motor? Any help is appreciated.:|

[rodbolt]

well a bit of maint as per the service schedule and this problem wont happen usually,
your symptoms indicate a failed pressure control valve grommet.
on the HPDI its a pain to clean and inspect the valve so 90% of the shops and techs simply skip it till it fails.
no water pressure sensor on that motor.
your symptom indicates a lack of wateer pressure in the block and normally it wont keep the stbd bank cool enough.
if your mechanically inclined its an easy service, if not DO NOT attempt it, if you breal the clip on the injector driver you get to spend 1100 on a new driver.
to access the pressure valve requires removing the injector driver,ECU and ECU holder.

[sledstew]

I own a repair shop for small engines,so I'm thinking I could tackle this,what should I watch for.

[rodbolt]

dont snap off the tabs on the injector driver when dissconecting it. its difficult to describe its uncliping procedure.
but if you dont pull it straight you can shear off the locking tabs.

[sledstew]

[whisper uid=32169]

Enter private whisper here

[/whisper]
I was wondering if you had the part number for the grommet you are talking about,my model # is VZ150TLRY
2000 HPDI 150

[rodbolt]

not here but if you hit the yamaha website you can find it, its on the exhaust housing. its under cyl crankcase. you will need the gasket possibly and the grommet.