Re: Volvo Penta SX drive 4.3GL
Without information regarding the size of your boat and drive ratio, I can offer the following suggestions.
I have a 19ft Four Winns Horizon with the same engine as you and an VP SX drive with a 1.55 ratio. My boat came stock with a 14.5 X 19 three blade aluminum prop. It allowed the engine to approach the high end of WOT at 4500 rpm.(Mfg recommends 4200-4600 rpm at WOT.) I recently purchased a 14.5 X 18 four blade aluminum prop to enhance my hole shot when loaded with the kids and grandkids. It definitely gets on plane faster, but my WOT went up to 4750 rpm (150 more than the mfg suggested 4600 rpm). While I don't run wide open very often this is not a concern for me.
Use Google to find prop retailers around the country, including iBoats, for prices and advice. Expect to pay $100-140 for aluminum and $250+ for stainless steel.
Hopefully this sheds some light on your questions.