I have a 22' flatsboat w/a 225 V-Max, my motor has always run high. I recently replaced the water pump and now I lose water pressure every time I break over on plane even jacked all the way down. Rough water (waves) does make a difference, more pressure. I replaced the pump assemby two more times with the same results. Since then I have replaced head gaskets, t-stats, prv and am at the end of my rope. I went to Port Mansfield, Texas and talked to the locals with Yamaha engines. They told me there was a design change in the factory pump and they had the same problems. Also stated they had spoken with Yamaha and was told Yamaha doesn't make lift pumps. Several of them replaced their pumps with an aftermarket Sierra and problem was fixed. I'm about to try it myself, anyone heard of this?
Buddy
Buddy