So you're saying on an 8X mph boat 20hp is worth approximately 2-3mph? That was my question about the speed difference in the 300proxs and 300R that I was looking for an answer on. Ironically the hp difference in the new V8 250 and 300 pro XS is only 20hp as well. Nitro gives conservative estimated speeds of their boats with different hp though they offer only one manufacturer, I was only asking for how much of an increase in speed is this motor worth over that one since a back to back test was done.