Fluctuating water pressure gauge.

I have a 05 Yamaha HPDI 175. Today I noticed my water pressure gauge fluctuating. Never notice it before. No overheating or anything. Any ideas? Thanks in advance. BTW this was noticed at WOT.

Could be your thermostat going bad. I had to replace one this weekend myself. Mine was doing it at low idle speeds, buzzer went off one time, my smart craft told me it was my thermostat, that's how I knew.

Ok that shouldn't be too bad. It would fluctuate between 18 and 25 psi. Was also a little slow to come up after getting into the throttle.

Check your intake screens first.

Poppet valve assembly needs cleaned or changed.

I have a 2002 OX66 225 and the pressure gauge never goes below 20 psi with the motor not running. When on plane it shows 60 psi.
Any ideas?

More than likely with the cold weather the gauge has frozen from trapped water in the gauge, see it alot this time of year and only solution is to replace the gauge. Or to I have seen if you remove the line from the back of gauge and it drops to zero there is a restriction in the line from the motor to the gauge if that the case find the restriction or just run a new line.....OPTI

Like Gary mentioned check the poppet valve could have trash in the grommet or the poppet valve spring is weak and not strong enough to hold the water in the block and pops off at a lower pressure or the poppet valve it self is worn and not sealing against the grommet.....OPTI

Tip during the cold weather. Disconnect the hose for the water pressure gauge and pour in a little RV antifreeze and re-connect. Enough will remain to prevent the gauge from freezing all winter.

Where is a good place to buy replacement gauges?

I'm having a similar issue where my water pressure gauge is showing 25 PSI at idle and doesn't go below that when running. My trim gauge isn't working either, so I guess I might as well replace that too.

I bought replacements for mine on EBay.