Stock you should be getting like 68 to 69 mph with just you onboard... easily over 65 mph at least! There's no excuse for it only doing 63mph at WOT that's nuts the non-supercharged 3-seater models do high 50's I've read!
Does your year model still have OPAS paddles? If so are we sure they are raising up at cruising and above speeds? Your rpm's sound very reasonable, it seems like you're experiencing drag somewhere somehow. Get under the stern and look at your intake grate and ride plate seams, are they filled and smoothed with silicone? I even filled the bolt holes in my intake grate with silicone and smoothed them over, as well as filling the ride plate bolt hole recesses. Anything under there that disrupts the waterflow is going to create drag. We don't want drag.
My 13/18 Solas Concord impeller is going to be slightly faster at WOT (18 pitch as opposed to your 17 pitch). The Solas website recommends a Solar Concord 13/18 for 215hp RXT's, and a Concord 14/19 for 215hp RXP's (though I truely believe the RXT should be able to pull that 14/19 also, as long as no more than 2 souls on board 3 souls might be too much though).
As I recall last August I was turning 7800 to 7900 rpm's at near WOT with the factory speedo indicating 68-69 mph on very light chop water at 25 feet above sea level roughly. That wasn't WOT, it still had a little bit more I could have fed in on that run (spark plugs crapped out without warning though). I haven't been out but twice since then and water conditions have been too rough to go over 50 mph. (sigh!) I don't have a GPS speedo, but that factory speedo can't be more than 1-2 mph off at most which would still put me going a bit faster than your WOT run. My speedo is NOT some 5 mph off! LOL!
What all have you changed out exactly at this point? How close was the new wear ring to the new impeller blades when you put them in? Mine were so close the blades lightly scraped the wear ring all the way around when I put them in early last summer.
What intake grate are you running? The OEM grate doesn't direct water to the top of the impeller, it only partially loads the pump as a result. Some people gripe that aftermarket performance intake grates cause drag, and they do to a small degree BUT they allow your engine to transfer far more power to the water by loading the impeller fully which more than compensates for any minor increase in drag the performance grate causes. I only rode my RXT a few times briefly with the OEM intake grate before I upgraded it to an Aquavein grate by R&D, and I never tried going WOT with the stock grate water conditions never permitted it. I do greatly prefer the performance intake grate's general handling characteristics however, the thing turns like it's on rails tight tight tight!
ps. When you say the supercharger has "no slip" I hope you are exaggerating because it's supposed to have a limited amount of slip by design.... right? How many hours and who rebuilt your SC? Your rpm's sound correct... but just for grins where is your engine oil level at on the dipstick right now? It should be right in the middle of the bend on the dipstick (why the heck BRP doesn't just stamp a full line on the stick I cannot figure... that bend thingy is nutso IMHO!).
- Michael
