Took the boat to the shop 2 weeks ago for the yearly tune-up (plugs, fuel filters, water pump, etc) and everything was working fine when I dropped it off.
Picked it up last Saturday and went to the lake on Sunday. Started the motor and noticed the water pressure gauge was reading 12 PSI. Normal idle PSI for my Yamaha 250 HPDI is around 2-3 PSI. I thought with the given conditions, cold water and air temp, cold motor and with a new water pump and housing, this 12 PSI could be possible and would drop down when the motor warmed up. Well, that didn't happen. When running at WOT the gauge was all the way to 30 PSI and when I killed the motor, the gauge would only go to 10 PSI. Called the shop on Monday and they said I must have picked up some trash in the line and it went into the gauge. They also said it was nothing that could have happened at the shop. In my opinion, I find it a little difficult to believe that I picked up some trash as soon as I started the motor at the ramp. The shop said I would need a new water pressure gauge (another $ 65.00 to the $ 675.00 already spent!). I've had boats for 25 years and have never had this problem. What do you think?

Steve I would chalk it up to the freeze as well. Had a lot of pressure gauges on swimming pools go bad because of the freeze.