I had the sea pumps changed and the star. motor water pump on my 502 Mag EFI's. I am getting 20 lbs pressure on the star. motor, and 35 lbs on the port motor. Wouldn't you think that the motor with the new water pump would have the higher pressure? Do you guys think I could have some type of blockage? TNT Marine did the service and said that "It is normal operating water pressure". Before the service both engines ran identical water pressure approx 20 lbs. I was thinking of pulling the thermostats and checking for some type of blockage.

I would pull the hose right before the first cooler after the pump. Feel in the inlet of the cooler & see if you find any parts of the old impellor floating around in there.

Mine had the same problem. A piece of impellar managed to get lodged in the therostat housing in the bypass area. You really have to feel around in it to make sure there is not a piece in there. If there is too high of pressure it means there is a blockage downstream of the block, at least with mine the gauges were hooked right into the side of the block. The only thing downstream is the bypass or the exhaust.