I will be running a 355 merc. with 490 lift, 230 dur. LSA of 108, with stock manifolds, 1.6 rockers on exh. 1.5 int. Am I looking for trouble? Guy at machine shop says probably not! As long as I blow out water before shutting down!

Yes, you have 14* of overlap. With stock Merc exhaust I wouldn't go over 7.

DAVE

I looked around , didn't see much in the way of smallblock manifolds! I guess I need diff manifolds and need to dump the water further downstream?

I'm at 110 LSA and Stainless Marine exhaust dumps 10 inches from the transom no problems.

Are you saying, go for it? I did find manifolds,but they weren't in the budget. I have 24' chapp. and can hardly find a place to go thru the hull!

Platinum, how far from the riser?

Miken- DaveF is right...it is overlap you should be concerned with. Wider LSA's will reduce overlap, but increased duration increases overlap...so, it's like dave says, its the degrees of overlap total. Now, is 7 deg. the magic number with stock merc manifolds? I don't know, but I'll bet it's close, maybe even a little less.
The best way to run your exhaust on an extended transom boat[like a Chaparral] is to run it out the sides...this gives you plenty of room to simply modify a switchable exhaust tip to run inline or you can run a 4" Borla muffler or similar...just make sure the muffler case isn't much longer than 12". Good luck!

Dave F so what is my total overlap with 224-234 110 LSA Thanks.

Sorry bout that Floridianson, I didn't scroll down far enough to see your name, my first time on the board!

Thanks, I'm in the process with corsa, but the question is, can I bolt on an elbow to the stock manifold to discharge the water further away,I was installing silent choice type, but it 90's right off the back, like 8-9'' from the end of stock riser? I know it would be easier to just buy a bigger, faster boat, but then I would have to make the garage bigger!