I'm in the planning stage of a build. 23' 5500# chaparral. Going to stay w/the sbc stroked. Currently have 350 mag w/270 hp. Would like new unit to be in the 450 hp 500ish tq. range. Will swap alpha w/bravo @ install time. I'm a 56 yr. old mature kid. No jackrabbit starts or wave jumping. Maybe pull grandkids on tube or skis. Would like to cruise @ 35-40 gps in the 3000-3500rpm area and top out @ 60gps. Have a FRIEND who is very knowledgeable about auto engines. Will you steer us in the correct direction for my setup. We understand about the safety issues auto vs marine. Budget to be in the 6-7k range. Is this a project worth attempting? Thanks in advance for your time. R. Mock

I would give cnc motorsports a call they can definitely build you something in that range. cnc-motorsports.com
Do you know the weight of your boat?
How fast are you running right now?

I have a friend with a 2350 SX chaparral with a 365 hp 454 and his will run low 60's at 4800 so you should have no problems getting the speed you want with that combo

Thanks for the response. Boat & gear weigh 5500#. Currently I'm @ 2k rpm= 20gps 3k= 30 4k= 40 with 42-4300 wot. 19p rev 4 prop. What are some of the more critical areas of my build. Will be using closed cooling. Are tolerances the same for a marine build vs. auto??? R.M.

do some searches on here - there's some very good information on your question posted. In a nutshell, I would hire an experienced marine builder to do at least the bottom end - go forged steel crank, h-beam rods, forged pistons, balanced and blueprinted. The extra coin is worth it if you want it to last. For what you're talking about you can probably find a custom builder that'll do an entire package for you for a reasonable price - it's standard stuff (not the same as a crate motor from someplace that throws them together).

Would the Dart 400 inch short block be a good start? If asked they will build it for a marine application.

Can anyone tell me the maximum safe idle for a bravo drive?(Will they shift in & out of gear @ 8-900 rpm? This question is in re: to the 383 build. Should i have used another thread. Thanks for patience. We have a long way to go here, don't want to step on any toes. Thanks R M

SHOULD HAVE BEEN IN THE DRIVE SECTION. Tried to cancel previous post in edit section & could not.

Hello, I did a 383 in my Sea Ray Pachanga 22 about 3 years ago. It made 453hp @ 5400; and started making torque @ around 2000(in the range of 420) cant recall exactly the peak #s was respectful #s.
Standard 4 bolt main block, GM crank Scat H beam rods SRP forged pistons, Balanced/ Blueprinted rotating assembly. AFR alum heads, Comp Cams springs, Scorpion 1:5 rockers. Used an Edelbrock- "air-gap " intake w/ 750 Demon marine carb. EMI Thunder exhaust MSD ignition. This was the basics, made reliable power started instantly, and it was run. Its not hard to make good power with parts "off the shelf" you can get all this stuff from Summit or Jegs.
Would recomend a Bravo drive, or spare parts for the Alfa.
The drive will shift @900 its really bad for the cone clutches. Try to get the idle around 750.

THANKS P/C22 Thanks R