Right...
I have a Chris Craft Scorpion 210 with around 600hp LS1 and Alpha 1 (with 1.5 ratio)...(yes I know its not going to last long...going to switch to bravo 1, propably...also looking into possibility to try Blackhawk )

The boat is still not tested with that new motor but did run 55mph (around 5200rpm) with the old one (mildly tuned 350 around 320hp) and with 21" pitch aluminium prop

Now the whole boat is redone and the x has been lifted 2"...

What would be a good starting point for a new prop? 24" to 26" or even bigger??
....I see that the mirage + seems to be the mostly recommended prop for the boat this size...

Jussi

I would stay with 3 blades to try to save your drive... good luck with that!

Mirage Plus 25 or labbed 27 would be my guess. I did a similar upgrade several years back... Formula 242LS with 454 Mag (365 HP/Bravo One drive) to built 496 (620 HP). Went from Mirage (non-Plus) 23 P to Mirage Plus 27 P. Top end went from 58 to 71 MPH. The bad news... smoked the Bravo One drive within 5 hours.

What rpm is the max power ?

Somewhere around 6000 rpm I guess...

Hmm...that's why I'm not so interested to swap bravo 1...I fear that it wouldn't last too long either...(but much longer than the current alpha1 will ;-))
I guess the XR would be a better choise...

The boat will be pampered and driven mostly at cruise...also no jumping will be done with it...so I'm crossing my fingers and hope that the alpha will last for one summer...

Juza

So it's all a guess ?


I'll guess a 25" Mirage + to start too.

GIGO = so don't hold us to anything.

On a more serious note, soounds like a cool project !

i think just the load from wide open run in glass will break an alpha with that much power. hopefully your torque number are small compared to your horspower. an xr should live fine behind your hot ls though.

edit: my guess is a 27

I haven't seen the actual dyno printout ...engine was dynoed by the previous owner in a -98 vette few years back...615hp was the output to be exact...with a little help from 8psi from vortech ;-)

The engine has ported heads, LS6 intake and A&A stage 2 cam....and now in boat ... Hitek stainless exhaust manifolds and through hull muflers (+3" H-pipe...a little trick from the car side to improve the sound, power? And pernhaps help with the reversion since I'm using wideband lambdas)

I'm using the same vortec V2 charger but with smaller 3,3" pulley (+and much bigger/efective water to air cooler) +much less restrictive air filter (just a metal grille over the intake funnel)...so I was conservative with the output numbers (or should I say estimation?)

I do have three props to start testing with...stock? Aluminium 21", ballistic 24" and really exotic adjustable pitch Supra S100 prop.

Juza

I had a 454 alpha combo, it didn't last one holeshot once all 8 cylinders were firing.

I went to a Bravo X upper and IMCO lower and ran the crap out of it with no problems.