GTX SC Down on RPM

[alexm499]

I have an 03 GTX SC with RIVA stage 1 kit installed last season. However I never got around to putting the recommended SOLAS 13/20R impeller in because it was late in the season and my stock impeller is in perfect shape. I just put the 13/20R in today and water tested, it's down 1 mph at 61.8 mph from 62.8 mph on the gps, not only that but it's topping at 7050/7100 rpm which is down from 7530 that I had with the stock impeller. If anyone can please shed some light on what happened? This is really disheartening as the impeller is $250.00 that put me behind in performance?!

Ps I also have the R&D anti cavitation aluminum pump come installed.

 

[alexm499]

Oh and I put a brand new wear ring in it with the impeller as well. I don't think I have any play in the shaft at the carbon ring (I do have a new carbon ring and bellows assembly sitting on the shelf just in case) spark plugs are New as of the end of last season and so is the oil. Oil level is dead center on the dipstick and the super charger was rebuilt with sea doo updated kit 20 machine hours ago.

Can the R&D anti cavitation cone reduce rpms by 500 with this set up? RIVA stage one actual kit does not include the cone so I'm wondering if I go back to stock plastic pump cone if I'll get the rpms back.. thoughts??

EDIT-- I put the plastic pump cone back on and water tested with solas 13/20R still installed and I was all the way down to 59.9mph and only 6950 rpm.. so that wasn't the problem. I'm going back to stock impeller for now I guess until I can get some information.