1993 Crownline 7.4L/Bravo 1 to 496/Bravo 1 Prop Sizing?

FuelishBehavior

Petty Officer 2nd Class
Joined
Aug 7, 2012
Messages
139
I'm about to stab my new 496 stroker into my boat. I'm pretty sure that going from 300 hp to 550 hp will require me to prop up. Currently have a 21 pitch that was right on the money for my original 7.4L which redlined at 4600 RPM's. My new 496 stroker should red line around 5600 with the hydraulic roller I've chosen and given the max piston speed of 4000 fpm that I don't want to exceed. I'm thinking one size up to a 23 pitch should be about perfect....I'm looking for anyone with their suggestion based on experience. Boat weighs around 4000 lbs, 1.5 outdrive ratio, assuming 12% slippage. Thanks for any insight...stainless steel props are expensive to use and be the wrong one.
 

Attachments

  • photo261405.jpg
    photo261405.jpg
    189.4 KB · Views: 0

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,470
Ayuh,.... I'd try the prop ya got,... spinnin' it a grand faster is Alot,....
 

wrvond

Chief Petty Officer
Joined
Mar 2, 2010
Messages
597
550 HP is almost twice what the Bravo I outdrive is rated for. You might want to consider going to a Bravo III.
 

FuelishBehavior

Petty Officer 2nd Class
Joined
Aug 7, 2012
Messages
139
REally? So you would stay with the 21 and not go up to a 23? I just don't want to chance over revving the new chunk of iron/aluminum. I'll give the 21 a shot then and if she starts to over rev I'll go up one.
 

FuelishBehavior

Petty Officer 2nd Class
Joined
Aug 7, 2012
Messages
139
As for horsepower rating, I was under the impression the Bravo 1 was good to 500-600 HP? I don't have actual data supporting this...all word of mouth. I don't do hole shots either so I figure with my drive shower, a relatively light boat, regular oil changes, I should be ok.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,309
Its the Alpha that is rated at 300

the 7.4 you pulled out was prop rated at 300, which is about 350 at crank

the motor you built is 550hp crank rated, which is about 500prop

I agree with Bondo, use the prop you got. if you're able to spin it to 5500, then adjust pitch.
 
Top