You really need to provide more info like current prop, rpm, speed, intended use ie. skiing or just top end... Anyway, for general use something in the 22" to 24" 4 blade thru hub exhaust will work. Probably a Merc Trophy 24" is probably your best bet. For top end an over hub 3 blade will work best, probably a Mazco RE3 26-28" or a reworked OMC SRX 27". Also worth trying would be a MERC 27" Tempest thru hub, as these are very fast and a little more flexible in use than the over hub props.
Good luck