i have a 454 330 hp motor and I'm running a 21 mirage and i am putting a air gap intake onit with a 750 dp carb and i have gil ex im putting on and going with a performance dis, should i change the prop or stay with the one i have? boat is a 89 245 ltd and in stock form wot is 4200 at 52 mph

Best way is to try the one you have, then you have a baseline. 4200 sounds a bit on the low side for that engine thou'. Don't remember the exact rpm range for the 330, but 4200 is not much. Have you ever tried anything else pitch and prop wise on the boat? Is it GPS speed?

yes on the gps,no i have not tried any other prop rpm should be between 42-4800 rpm i think

ttttt

I would just try the prop you already have to get a baseline on your changes it might put you up to 4800 where you should be

thanks thats what i will do