HELP with prop selection
 

I'm getting ready drop in the new motor. A fresh Mercruiser 454/330 with roller lifters and rockers, double spring valve springs. Edlebrock intake and a Holley 750 Marine carb, 4" Stainless Marine thru hull exhaust with a Bravo One. I went from twin 350's to a single BBC. I'm guessing the weight didn't change much. Stock weight was 3450 lbs or so. I have three props 25, 23 & 21 pitch. Which prop should I run and what kind of speeds should I expect to see? I heard the 454 turned a max of 4400 rpm's. Any advise would be greatly appreciated.

the 330 454 can run to 4600-4800, i'd start with the 21 and go from there, i want to say the preferred rpm is 4200-4800, just watch your r's and take a gps along

Here's the factory info on my boat. This info was taken from the Chris Craft Stinger registry. Says the 260's weight is 3450 dry. Which prop would you guys recommend the 21, 23 or 25 pitch. Also do I need to install a thermostat? I do not have an enclosed water system just the pickup on the bottom of the hull.

1982 260SL Stinger
Length 26'4.5" 8.04 m
Beam 96" 2.44 m
Weight 3450 lbs 1568 kg
Fuel Capacity 128 gals 486 lt
Fresh Water Capacity 8 gals 30 lt
Color Options:
Ivory with Blue/Blue Accent Interiors
Ivory with Brown/Brown Accent Interiors
Ivory with Burgandy/Burgandy Accent Interiors
Power Options:
2-260 hp Mercruisers 1802 lbs 819 kg
Top Speed:
2-260 hp Mercruisers 60 mph
Base Prices:
2-260 hp Mercruisers $37,595

BH, Thanks for the reply. Is it the lower the pitch the higher rpm/speed or do I have it backwards?

the lower the pitch the better the hole shot but you will lose top end, this will increase your rpm's, higher pitch will slow hole shot increase top end as long as you can spin it at the desired rpm's, 2-300 rpm change is average for changing pitches, the number of blades also changes the pitch needed, example is a 25p 3 balde will spin roughly the same as a 24p 4 blade, labbing a prop always nets best performance and usually you can spin a larger pitch in the same rpm as the smaller one

pitch is length. how far boat travels (thoeretically) in 1 revolution of prop. each 2 inches of pitch is just under 10% change in WOT rpm's. big blocks outweigh small blocks by about 150-200 lbs. bravo outweighs alpha by 50 lbs. but you only have half as many motors. back of boat lost at least 300 lbs, maybe more. so check tongue weight before towing very far. you might be nose heavy on trailer.

Thanks you guys for your response, definately helped...

For the size boat and HP I would start with the 21. Not familiar with the boat, but my guess for speed would be 55-60 with the right prop.