Ok guys I'm in the process of deciding what I will use to power my next and hopefully final project.
It's a 1985 Scorpion 24' that weighs approx. 4500 - 4700 with engine, drive, fuel etc. It currently is set up with a 454 400 cyclone and TRS.

Core Requirements: 75 mph and as reliable as possible.

I want to know what would you do? I'm thinking a mean 383 or do I go 454 or 502? Give me all your input.

Please pass the popcorn.

There is no substitute for cubic inches.

You will get more bang for your buck with the big block. But I am in the process of installing two 383 MPI's in my 23' Formula. I am a small block guy at heart..... comes from many years of oval racing.

There's no replacement for displacement..... except for RPM and airflow.

A 8000 RPM small block aint gonna work in a boat, so you have to supercharge it to get that kind of power.

Cuda beat me to it. I'd go 502. BOB

Ok.. Ok.. cubes it must be then.
I knew there was a reason those GM crate 502's kept on looking at me..!

I have a 468 that was just freshened with all new bearings, new moly rings, oil pump and valve job. The internals are all forged and excellent parts:

Gen VI Block

JE Pistons

Scat Forged Crank

Eagle Rods

Dart Heads - Iron Eagle

Rev Valves

Crane Gold Rockers

Hydraulic lifters

Your choice of Cam

Flywheel, Aluminum timing cover and Steel Oil Pan included.

This engine is balanced, blue printed and assembled.

$ 6,200.00. More HP than a stock 454 or 502.

Kirk

basicaly it comes down to power to weight. to move weight you need torque and that will only come from cubes. reliably anyway's. small blocks are great for say a 22 velocity or donzi. but i would think a 500 or 525 would do it with great resale and reliability.

My 502 MPI Mag ... 500 EFI cam ...Crane Roller Rockers ...good exhaust ...= ~ 500hp .....

The Square Root of (Total Shaft Horsepower / Weight ) x Constant = Speed

Square Root of (500/ 4700 ) x 250 = 82 mph

Drop it in .. turn key ... go ..... 7000.00 delivered ....

Last year I built a 383 that should put out 400Hp (no dyno #'s but a extremely similar build put out more with worse heads)

However, I have more $ into than a crate 502

Just like offthefront says.

I'm not sure about your math. Square root of (500/4700)*250 = 5.16

Is there something missing in your formula?

EDIT: OK, square root of the function (500/4700). I guess that's why the parenthses! Duh!