@espnman A couple things seem odd.
33.7 mph from 3025rpm does not sound right. Most older boats with 1:1 ran a 13x13 and 32 was ~3200, 34 was ~3400 and so forth. Boats with reduction gears ran bigger props and higher RPM. What boat/prop do you have? Sure your getting 33.7 from 3025?
PP Classic is rpm based, has no idea about speed. The "MPH" in PPC are just labels assigned to a group of settings. Key are SSD, Baseline RPM, Wind Adjust, Crew Weight, Skier Weight, Kx and Px (switch). PPC also needs magnets. Not just for timing but to trigger SSD but seemed to chase time as well as RPM (seemed to give hot segments after slow segments). Setting baselines out of course, no magnets so no SSD, seems you are setting for a "out of course situation". Go "in course" with magnets and SSD comes into play and different result (speed). Checking out of course may be root of speed issue, just a theory, been a long time since I have run PPC. Used to be quite good at it.
As far as your skiing perhaps the month off so rusty plus water temp change was enough for this issue to bite you. You just managed it in summer.
So, dumping everything else, what times are you getting in course for 1 ball, 3 ball, and end time? ABT is best but those three can illuminate whats going on.
When I was in WA State in spring we would take boats from the Western side to the Eastern side chasing heat. Left 50ish water for 80ish water. Temp and mineral content difference between the lakes necessitated we reset baselines. Drop boat in and go reset. Same before tournaments then, checked and set every boat every speed baselines, in course with ABT.