200 HPDI losing water pressure at higher speed

[Southern Basser]

Just had a new water pump kit installed at dealer, put 5 hours or so on engine since, ran fine. While fishing Saturday, at take off boat only got to 60 mph (normally runs 67) then started losing speed, looked at water pressure gauge and it was 0 and had alarm. Long story short, rest of day if I stayed under 3000 rpm's and engine trimmed down I had 7-8 lbs of pressure, if I trimmed up and ran faster, lost all water pressure. Water still coming from pee hole and no miss. I called it a day at lunch fearing potential damage. What do you guys think before I drive 100 miles back to dealer?
Thanks

Engine at 3" below pad.

[JOHN202]

Sounds like it got too hot. You need to take it back in asap and get them to check the work they did on the water pump,then check the motor itself.I would not run the motor at all until thats done.

[Neilslure]

When my motor was new I would have water pressure until I hit about 50 MPH, then it would drop to nothing. It turns out that the plastic grates on the lower unit were a little loose and sticking out enough to cause water to go around instead of in. It might be worth checking before you haul it back.

[Southern Basser]

Thanks Neil, you were right on target. Took the grates out, cleaned, re-installed tight and flush, water pressure great.