I see this becoming more of a trend as volume of donor engines become available. I'd be up for it.

We had a 21'barefoot ski boat here. With a dart alum block 406 stroker lingenfelter heads hooked to a volvo duoprop.raw water cooled. It was a odd duck but could obliterate contemperary v drive flatties and jet boats in a drag race . The good aluminum that goes into those castings holds up fine in fresh.pickle in coolant in the off season. Several hundred pounds off the ass of a several thousand pound boat will make it pop up on plane quicker.if you have the money go for it.contemporary small block non catalyst exhaust is out there to support the power

I'd be all in on some LS6 action in my boat. They are 405 at the crank with a fairly mild cam from the factory. Do a cam swap, change the intake and roll with it.

Lighter is better, but what about balance? Eventually they become so light in the stern the bow pushes. I took cast iron intake and exhaust manifolds and replaced with aluminum. Boat wasn't really any faster but planed easier. Took off the 125 pound swim platform and had trouble lifting the bow and prop blew out. Went bigger diameter on the prop but still 1-2mph slower.
Weight in the back isn't a huge deal as long as you plane ok

We just pulled 541HP out of my C5 Corvette with an LS1 earlier this month. They are amazing engines. There is a reason why they are the base starting design for Seven Marine.

Volvo Penta is going to all aluminum blocks and heads and so on - all based off the newer GM Gen Direct injection engines. Just an FYI

Someone else here on OSO with the same idea...

http://www.offshoreonly.com/forums/f...esnt-work.html

You can build some potent packages with the LS platform. It's all about how much you want to invest. You can build a 450HP engine on a budget, or go off the deep end. I chose the ladder.

http://i1375.photobucket.com/albums/...pscktusl1w.jpg

My next boat will be a 34 Powerquest Vyper. I will end up putting twin procharged LSx motors in it. Probably start off with newer 6.0 truck motors with Iron blocks. That project is going to happen sooner than I had originally anticipated. I'm done with BBC for a while haha.

I would not mess with the std small blocks at this point either, yes you can get the H/P up there easy enough, but the torque is not there, seen all kinds of claims, but also seen boats that people pulled big blocks and did high H/P small blocks...no many really happy. Now the LS is a totally diff deal, a iron block 6.0 produces great torque and power...add boost and works awesome...If you decide to do anything that has aluminum block or heads, closed cooling is a must, even in fresh water these light weight parts will get eaten up quick..