What a learning curve I have had on this issue!!! Sherm had told me what to do on the first trip out in the boat, being hard headed and having Yamahas with lower water pickups my last few engines I battled the low water pressure deal for 6 hours. I went as far as taking the boat to the shop, I got lucky and a Merc Tech Rep was there to hook up to the engine and go over EVRYTHING with me. That darn ECM will tell EVERYTHING you do with your engine. Good thing it was broken in my the book with a factory Tech Rep being the first person to hook up to it. I am at level plates, actually today I moved back to 1/8 over level since I am figuring out what I need to do when cruising in the mid range. You MUST trim that motor down to get a minimum of 10 if not 12 PSI at 4-4500K if you want to keep from overheating. I am only getting about 15PSI at WOT, and 1PSI at idle. ALL normal per the Merc Tech Rep on this motor. With just me in the boat I have hit the rev limiter once, I can bump it all I want if I over trim, still running the 23 Tempist that came on it. I plan on trying a 24 soon. With two people in the boat I am running 5650 RPMs and 60.5 MPH FULL tournament load including livewells. Today I was bumping 62 MPH at 5700 RPMs and 15 pounds of water pressure, 90 degree water temp in the block. IF I COME OFF WOT I MUST TRIM DOWN before lifiting the throttle, if not the rear of the boat pops up and I lose a few pounds of water pressure and within a min get an overheat. With some seat time I am finding I get better speed not trimmed to the max anyway. Good luck hope this helps answer some questions.
.
