I am having the EXACT same problem. I have 29 with HO's and was getting 5200 at 78 on GPS....I recently had one drive worked on and during the process they switched the drives from one side to another to check something out (long story)....They left the drives switched which they indicated was no big deal....Bottom line is that both drives were off the boat at one point.... I'm now getting about 4900 and 74.5 GPS. 26P Bravo's......This is loss of 3 or 4 MPH with same conditions, load, etc...The driving indicator is showing one drive higher than other.....I'm wondering if they placed the stop in the wrong spot or if they didn't align the drives correctly, or other issues????? While 3 or 4 mph isn't the end of the world, it sure bugs me.......thoughts guys?

Update.....Re-aligned my drives and threw on some K and N filters (thanks Trick Marine). Now I can turn my 26's at 5k rpm and hit 73.4 gps. Fastest prior was about 72.

damn, i didnt know the drives out of align slowed you down that much. maybe i should check mine