Many car performance engine builders thought/think the exact same thing when entering the I/O boating world.

How hard could it be...right ? Well.........

Exhaust and water is one thing - and yes it is big! - but there are many other items (as I've mentioned) that will bite you in the butt if kept on the automotive theme.

Steep learning curve - better not done at the customers expense. Or in the case of the DIY that's built 1 or even many performance car motors, homework and experience is advised before jumping head in. These I/O (offshore) forums are chaulk full of people (edit in : engine builders and DIY's) destroying equipment (motors, etc) and being served lots of humble pie from the assumption of "what can be so different."

Anyhow....... that's just the way it is. Hope this helps.

I think if you use the right clearances, head gaskets, exhaust valves, and oil pan, and of couse if the customer keeps the water out of the exhaust you can be sucessful, I have been.

I did a 330hp build last winter and i got robbed somewhere along the line.
I used bob mandara cam w a .6 lift cam, and 781 heads ccd by head shop around 113-115.
The motor is in a 24 pantera which i read do 75mph with na magnums, I went from 58 to 64 mph max after rebuild. Rebuild included forged domed pistons, morel lifters, bobm cam, 781 heads. I alreads had sm exhaust. Im currently in process of installing some oxgen sensors to get jetting a little better bc im on the rich side

I thought i was going to have a radical motor but i couldnt get this motor over 5000 rpms with a 23 pitch prop 3 blade,
makes no sense

I remember your build, did you leave it a 454 or go to a 489/496? The 454 should make about 480HP, stroker motor about 520HP. Don't believe what people tell you about how fast there boat goes. Even when I pass people they tell me they had throttle left LOL

Car engines and marine engines are completely different animals. I'm assuming vortecpro is the same vortecpro from the chevelle site. When I built my last engine i consulted with many people on the build of my 427 (440 CI) marine engine. Of which one was Chris Straub from the Chevelle site. He said there was NO WAY i could build more than 425 hp out of that engine and have it work in a boat. I ended up letting Bob Mandara spec the entire engine. We ended up with right around 525 hp at 6100 RPMS. This pushed my Formula 242 to 68 MPH. That said I find it VERY hard to believe that your going to be able to build 550 hp in a 454 with peanut port heads that will work in a boat, possible I guess but highly unlikely. There are lots and lots of variables that are MUCH different than an automotive application.

My new build engine is 468 with stock bottom end, 088 heads, Isky 270/280 mega, 1.7 roller rockers, Edelbrock intake and 750 marine carb. Made 407hp at 5000rpm and 474ft lbs max torque at 3800rpm on the dyno at Orlandi Performance.

Dry exhaust...108 lobe center? compression?

Wet exhaust, 114LC its not a big cam I didn't want to worry about reversion, 8-1 comp but might be a little higher heads were used and we shaved a little off. Below is the link for the cam specs.

http://www.flatlanderracing.com/iskycamsmarine.html

that motor could tolerate more compression,some horses hiding in there

Yep, I thought it would make more. I'm happy with it for now it was my first engine build. The stock 330 decided to eat the number 7 exhaust valve last year. It's got about 12 hours on it now and I'm trying get the right prop on the boat for it before it goes into storage.