Water pressure gauge

[selmahotrod63]

My 2006 VZ200 HPDI water pressure gauge reads just 10 psi at 5000 rpm. I bought this boat used. No cooling problems. Is this normal?

[fairdeal]

without knowing exactly where the gauge is connected, not to mention how accurate the value is
(doubtful it has recently been "calibrated to a NIST traceable standard")
the gauge value can't be "taken as gospel"

on its face, seems a few psi lower than I might expect.

but it would be "normal" for a water pump impeller, in service for some time, (perhaps many years?)
to produce a lower output pressure than a new one, freshly installed.

so no immediate cause for concern.

But - IMO - as new owner of a used, older motor it would be prudent for you to do several things

- make sure your audible alarm works: pull the safety lanyard and then crank the engine, you should hear it

- at your earliest convenience, drop the LU and open up the water pump for inspection.
This does several things:

- ensures that the LU can be removed (sometimes they are allowed to corrode until they are stuck)
- lets you evaluate the condition of the impeller and pump housing

[boscoe99]

The specification from Jamaha is 11 psi minimum at WOT.

Better to be slightly below specification with no over temping issues than to be above the minimum specification with a motor that is not being cooled properly. IMO.

The VZ200 model has only one pair of forward water inlets. Those inlets can be a but fussy at times. Some folks have been known to have to raise the height of the motor on the boat in order to get better water pressure. Contrary to normal thinking. Usually at very high speeds if one drives around like a maniac like VZ owners are known to do at times.

[rodbolt17]

the difficulty level to access the pressure control valve usually means it has never been serviced.

[zenoahphobic]

The specification from Jamaha is 11 psi minimum at WOT.

Better to be slightly below specification with no over temping issues than to be above the minimum specification with a motor that is not being cooled properly. IMO

The point being: that a pressure gauge measures pump output pressure against a restriction.

Low might mean poor pump pressure or there is excessive restriction between the pump and the gauge.
High might indicate good pump pressure or there is excessive restriction after the gauge.

The problem is we don't know which. Overtime we have a failing pump and increasing corrosion or salt clogging in the cooling passages, as the two have an inverse affect on pressure we may very well see the gauge still read normal for some considerable time although cooling is deteriorating.

This is why simply connecting a gauge somewhere is not much better than useless. You need two points to measure from to monitor the change in the differences in pressure to ascertain changes in the cooling system.

[99yam40]

the difficulty level to access the pressure control valve usually means it has never been serviced.

I am curious as to how the Pressure control valve could affect the water pressure causing it to be low at high RPMs

[selmahotrod63]

Thanks for all input.