Re: 383 / Alpha prop selection
 

john,
You will want to try a three and four blade prop on your boat before you buy because there will be differences in the performance. I have a similar size/power/weight setup in my 20' Sutphen with 7.4/Bravo and most of the time I run a worked 25 Mirage 69mph @ 4800rpm. The Mirage is the most fun, particularly when running alone. The backup Bravo is best for carrying a load, midrange cruising and staying on plane.

Re: 383 / Alpha prop selection
 

Was able to borrow a 14 x 24P, 3 Blade Ballistic ==> want to find out how close will be size / pitch wise for starting reference. Hope to try in couple days.

Re: 383 / Alpha prop selection
 

Just curious... what did you put into your 383? How did you have it built? I would have expected a TON more torque for a 383... even really mild. My 383 with ported vortecs on the dyno was over 450 ft lbs. with 400 ft lbs available "forever" across the rpm range.... if I remember correctly (the dyno sheet is buried in my office stuff that I moved from DC), it was building 400 ft lbs from 2k rpm on!

Re: 383 / Alpha prop selection
 

TOMZ

You are correct. Wouldn't take much to >> increase HP & Torque in the 383 application. Wanted increase from stock 2Bbl 5.7l, but scared to death of crushing the Alpha. Will have to look specifics up, but went to one over stock w/a Comp Cam, heavier springs, CI Merc Manifold (plugged injection ports), 600 cfm Edebrock...
Good overall performance incr w/o killing reliability of the system was the goal. So far so good.

Re: 383 / Alpha prop selection
 

I ran a BB chevy on my alpha with no ills being easy on the throttle....Back to a roller 350 and wodering how that Ballistic prop works out. I have a 22' Pachanga with a 25 Mirage that runs 55 @ 4500 rpm and pops right on plane.....I bought a ballistic 21 or 23 and haven't tried it out yet....

Re: 383 / Alpha prop selection
 

I have a Pachanga-22 running a Mirage Plus 25p and GPS at 71 at 4750 RPMs.

Re: 383 / Alpha prop selection
 

Bigjim,
Is that a small block? Bravo or Alpha and what gear ratio?
Ken

Re: 383 / Alpha prop selection
 

1.5 Bravo with a 496 :D

Prol selection
 

hi I have a 24ft crestliner nortic, when fully loaded we are about 6,300lbs just shaped engine to a 383, with 425ftlbs from 2k and on rpms and 398hp at 5500rpm. We have an alpha one with 1.84 gears and a 14 5/8"x 23p 3 blade prop and get to 42 @ wot 5500 but have lots of throttle left? Any ideas on what prop I should get. Thanks

Your Alpha gear ratio is set up for a V6 190 hp stock mercruiser engine.

Gear ratio also effects where peak torque will land for rpms.

Most marine engines peak torque lands around 70 - 75 percent of max load.