formula1

$4,000 is estimated cost of a pair of CMI's or Stainless exhaust for a twin small block motor application. You might've missed that part of it woody1!

But, it sounds like you have a nice motor for your single engine boat.

woody1

Oh ya I did notice the twin engine but had a brain fart, still 4k for exhaust on bone stock longblocks is a waste of money in my opinion. I would put heads, cam and intakes on both 350's before exhaust, would would obviously reap much much more than exhaust and come in under 4k on top of it all

formula1

I know what you mean woody1! LOL! That is why I started this thread. Seems like it might be better just replacing the manifolds with stock ones. This isn't going to be a "race boat". But, if the aftermarket manifolds produce good enough gains, they might be worth paying the difference. From what was posted earlier, 12hp per motor is NOT worth spending $16-1800 per set...almost $4000...for 24 hp!

woody1

Exactly, here is a perfect opttion and what I would do if I were you. something like this, I dont know what your setup is but this setup would save 200 lbs on a twin engine. http://cgi.ebay.com/ebaymotors/ws/eB...3ARTQ%3AUS%3A1

Droppin 200 lbs is a hell of a lot of weight

David Stotz

If you search these forums you will find plenty of info on SBC marine exhaust systems. I think your missing the point. You need to look at your motor as a system. Just changing the exhaust is not going to net great horse power gains. But if you change the heads, or intake, or cam, how much do you think the stock system will hurt performance? The other benefit of these after market systems is that water does not pass between the manifold and riser. By the way I just purchased a set of Stainless Marine exhaust for my SBC. Brand new manifolds, slightly used SS risers ( they look brand new, no scratches ) and all the hardware for $1150.00 from an advertiser on this board. By the way Woody what exhaust system was on your motor when it was dynoed?
Dave

David Stotz

I just saw your post for the Moore system. That's interesting, I just spoke to Dennis about a month ago and he told me his system is no longer available!
Dave

woody1

I just happen to run across that ebay auction, says he has 10 of them sets and cost 30 bucks shipping. I just used some equal length headers on the dyno. I expect to lose some numbers once in the boat. but the engine has a ton of room for expansion once I see how the alpha one holds up. Im a big inch Ford guy and this is my first time building small blocks, chevy small blocks nonetheless.

formula1

I understand that an engine is an air pump, basically. But, as I stated earlier, this is not going to be a "race boat" nor do I ever have plans on doing any expansion (of course, things change). HOWEVER, since it looks like I need to change the exhaust manifolds and risers, I was wondering if it was worth spending the extra to get some GOOD aftermarket sets. Otherwise going with the stock setup is probably fine for me. I'm just looking for an excuse to get some CMI's!

Thanks for the link woody1. I suppose something like that would be my best bet...

woody1

I think so, I just talked with Dennis and they are an exact replica of stock merc's just in all aluminum, and the riser gasket is the graphite one so I wouldnt worry about leaks. Go ahead spend the 1000 for the pair and send me 500 for saving you 2500

pullmytrigger

After 3 yrs of researching.....looking for used......claimed and real performance gains....wieght savings........price and bling factor........I just bought two sets of polished sbc Rev Marines from Fred at Trick......its over!!!!

and whatever you do make sure you get all nessesary brackets