How are you intending to use your ski, raceing vs recreational? A stock impeller on your ski consumes about 12.5 gallon of fuel/oil at WOT,with a stock 15/21 pitch impeller. Load also is a varient to concider. Sometimes changeing a pitch angle &
duration can dimenish performance, so I suggest your talk to a manufacturer rep,
after you remove your impeller to inspect if its an aftermarket or stock.