@MopedMedicks I'm no expert, but there are other factors that could be causing that speed difference like deformities in the hull, weight, gas tank location and shape, even shaft alignment. Also, can you describe how you could "see" the 1.5" difference in engine placement between the 2 boats parked next to each other. Did you measure?
BTW, I still have a 99 RLX and a friend had a 98 and I never noticed a difference. Can't say I ever actually tried to notice though.