I Know they won't endorse the idea. I'm just wondering what the differences are between their marine offering and street version. Is it just the cam and compression ratio (and probably head gasket and freeze plug material) or do they clearance the bottom end differently.

The 502 I have spun a bearing. I was about to drop it to the machine shop when this marketplace 632 popped up. I'm assuming the crank is toast so I thought might as well put a bigger crank in it. Im not looking to go 100 mph. Maybe mid 80's so i can cruise fast. Its hard to get a straight answer on how much power that will take with my setup. I think 750Hp will do it but we'll see. Thanks for all your help. I'll check out that blower. The snout might be all up in the back seat lip.

we run a sort of similar boat a 25 or 26 thunder xr drive and basicaly an open class 540 na right in the 800hp range but we killed torque down low and let it wind up over 6500 its a blast fun and stable and reliable

If Im reading their description correctly, yes exhaust alignment issues............300 + .700 = approx 11/16 of an inch. ........thats a big thumper cam, Id get a dyno sheet and find out where it makes peak and torque.........my guess is peak hp is in the 6500 to 7k range

OK I read it as the exhaust is .300 higher, just over 1/4". I didn't realize you added it the deck height as well.

I just talked to BluePrint. They said they've had quite a few people run this engine in a boat with "great success". He knew all about reversion and sad that street Cam is borderline so keep an eye on it. The only difference between the marine and street versions is the cam and a thicker stainless head gasket to dump down the CR a bit.

I was going to mention possible head gasket change to lower compression........... 10.2 vs a 9.8 deck then ad the raised ex port is a pretty good jump.............plus the tall deck is a little over an inch wider, but its doable with custom tails

CMG223,

Not that we don't all love Roots blowers, but I'm betting you'll never get that blower under your lid, given it's got a carb and breather on top of it. The Whipple is going to be a more likely candidate, as long as you go EFI, as the intake is on the back of the blower, not on top. They also generally have a flatter torque curve than a Roots with a higher effective RPM range. the Roots are low end torque monsters, but they run out of steam at higher RPMs. they also typically use narrower rib belts as opposed to cog belts, which might be just the space you need behind your seat.

If you are ultimately limited to NA, my reading and listening would lead me to advise against the 632. Just too high a rod angle. There have been guys do it, but I think it's always been to less-than-stellar long-term results. A well-built 540, or 565 if you can squeeze it out of your block, will suit a marine application better. I know my dream engine would be a Dart BigM 565, 4-3/8" stoke and 4.530" bore, hydraulic roller build. But I'm stuck with an otherwise stock 496/8.1 GM block and heads, and a CFO that has already discovered the edge of the checkbook and doesn't feel she needs her knuckles any whiter.

Thanks. Brad.

Thanks Brad,

That's good to know about the rod angle. I'm hoping to keep this a fairly budget orientated build. Thats why a Big cube Dart block or EFI whipple set up was crossed off the list early on. Ideally I'd like to use my gen 6 502 because I already have a carb and intake that would work. All my accessories and exhaust would transfer over. I might just stick with that route. Go buy a 540 rotating assembly, a nice cam and some decent aluminum heads and see what I can do with it. I just didn't want to spend a bunch of money and in the end wish I had another 100Hp.
Its kind of a unique setup so figuring how much power it'll take to go 80-85 isn't well documented

Thanks
Chris

Good to know. My CMI's are the 1 piece header/tail combo so there isn't much wiggle room at the transom. Thanks for the info.