2 blade prop selection

[sonny glide]

I have a 72' bubble deck,
575-600hp 406sbc w/3.75 stroke
presently have a 10deg box w/15 gears and a 2blade 11.25x16 prop
will it work?
the motor needs to see 6800-7000 to make that hp< these super mouse bullets turn over 8 on the strip so the bottom end is set up to handle it:jawdrop:
if not where do I start 1st?
A: turn the prop down to 11.0 / 10 7/8
B: go to 12's from 15's

[Lookin for Liquid]

Only one way to find out!
Looks close tho......I have never been a fan of reducing prop diameter and if the 11 1/4 bites too hard try dropping the gear so it see's more power. Maybe other people on the boards have some experience with small block torque characteristics....but until you try it you will never know for sure.

[Moneypitt]

The 3.75 stroke puts your motor in the "under bored" BBC range. A 427 is a 3.76 stroke, but also a 4.250 bore. I think the gears are close, but the prop is too big in diameter and pitch. If it feels weak down low try an 11X15. That may "crutch" the engine into it's power curve of 6K plus.......We pull 7800 out of a simular HP BBC, (440) with an 11X15 and 25s in a Revenge circle hull...MP

[sonny glide]

dogge down low change the prop to a 11x15 1st, and leave the 15's in the box??:idea:

[Fiat48]

Bear in mind a boat loads (drags) a motor a whole lot more than a car does. How free the boat is, bottom design etc is a large player of what rpm the boat will let the motor see.

[jimthetoolman]

Hey Sonny Glide I have a 10 3/4 x 15 2 blade forsale. Let me know if your interested.

[PGF500]

I agree with lookin for liquid. Drop gear! With a 11 1/4 and your hp and torque I'd try a 9 gear first then start cutting on the prop. Maybe take a little leading edge away so it doesn't bite as hard. You have a couple way you could start.

[sangervdrive]

Can I ask a retarded question from a beginner?
I'm gonna anyways, Why do we run two blade props? to save weight? less drag? My only other thoughts are that it might have to do with the low pitch compared to like a mercruiser setup.

[Racey]

Can I ask a retarded question from a beginner?
I'm gonna anyways, Why do we run two blade props? to save weight? less drag? My only other thoughts are that it might have to do with the low pitch compared to like a mercruiser setup.
2 blades don't lift the transom as much as 3's, making the boats take a better set at higher speeds. the trade off, a little more vibration, and not as good out of the hole, however with the right 2 blade you have no problems getting her moving out of the water.

[suckerpunch]

We have a customer that has a small block powered hondo ,3/8 runner. It is heavy.It has a stout 406, that can rpm. We put 1.09 percent in the box, and it runs one of our river racer props,narrow ear, that is 10 7/8 x15. The boat flashes at the hit, 6800 and climbs to 7800 in about 1200 ft. it runs 96 mph. that to me is pretty good. the engine has a really good set of heads. This does not mean it will work for you, but I think that the advise to drop the gear is good. everybody always over gears, and than they get spanked by jet boats.