Ron, the K&B 3.5' OB's I used to own came with two metal props. Almost looked to be galvanized steel. Strange huh? The Prather Tunnel kits came with a P275ss. This was 15 years ago, so they might've changed things. But I remember running the stock props for kicks and giggles and they would not plane out the boat no matter what engine setting... burried or surface.

The only plastic/carbon props I see used are on the MHZ Z'drive and the cheaper electro boats.