I think one problem with the setup is the difference in the engine weight in the back of the boat. It should slip more with an Ilmor. When big blocks were removed from my velocity and Ilmors installed the boat was sitting about
2" higher out of the water. The major difference between the
merc's 600's or the 700's is the Ilmor has an advantage of about 30 to 35% better fuel economy.