2003 Yamaha 250 VMAX 0S66 water pressure

[sammie4516]

Water pressure with this motor starts out at around 28 to 30#,s drops to below 4# when RPM gets to about 5800. It runs for about a half mile then shuts down. As long as the RPM is at 5400 or 5500 the pressure stays around 12 to 15#'s. Flushed everything with no change. Changed the water pump with no change. Had a 4 blade prop on it switched to a 3 blade with no change. Any help would be appreciated.

 

[99yam40]

water pump sucking air or exhaust would be my thoughts

have you changed anything up on this set up lately?
has this rig ran fine before

 

[sammie4516]

Changed nothing. Just had a new water pump installed last week. Don't understand why it pumps fine at 5400 RPM but at 5800 it his to less than 4#'s.