I recently purchased a 200 SHO. After about 9 hours of break in I started having water pressure issues. I was running around 5000 rpms and water pressure was right above 23 psi. Water pressure started dropping. it dropped to around 13 psi and then back to 23. It continued doing this all the way back to the ramp. I took it back to the dealer. They went through the lower unit, changed the impeller and some screens on the lower unit. Next time out it continued to fluctuate as before. I talked to the dealer again today and they said the Yamaha tech said that as long as it dosent drop below 11 PSI it would be ok. I have never seen a motor fluctuate like this in 25 years of running a bass boat. Any suggestions on what would cause this. PS: I pressurized the line from the motor to the gauge and pressure held so it is not a line leak or bad gauge. The dealer preformed the same test with the same results.