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Exhaust Gains

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Old 02-28-2008, 11:09 AM
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Default Exhaust Gains

What kind of gains have you seen by adding an exhaust? What kind of boat did you put it on and which engine. I am looking at adding an exhaust to a 29 V with a 496 HO and am wondering what I'm realistically going to see, maybe 2 or 3mph?
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Old 02-28-2008, 11:35 AM
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Changing only the exhaust won't change anything except your bank account.

An exhaust change should be made in conjunction with other changes, like supercharging.

As a basic rule of thumb, you should only pay for performance upgrades if you can get 1 mph for each $1000 spent.

Good luck!
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Old 02-28-2008, 12:46 PM
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The CMI's for the 496 HO's have shown pretty gains on the dyno over the stock system. They claim about 60hp, I think. Not sure if its true or not or the dyno numbers will transform into actual speed gains.
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Old 02-28-2008, 12:50 PM
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A guy with a 22 Donzi was saying he didn't gain much if anything with the 496/CMIs. I'd think 60 HP in that boat would yield at least 3 MPH.
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Old 02-28-2008, 01:39 PM
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i'd only upgrade an exhaust if the current one was shot.
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Old 02-28-2008, 02:05 PM
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I had a 454 mag 385 H/P changed from stock exhaust to imco power flo exhaust and gained 2 + mph on a 1997 22 foot scarab
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Old 02-28-2008, 02:45 PM
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Quote:
Originally Posted by trc2 View Post
I had a 454 mag 385 H/P changed from stock exhaust to imco power flo exhaust and gained 2 + mph on a 1997 22 foot scarab

Your gain was probably 1/2 and 1/2. With 1/2 of it coming from weight loss, and the other 1/2 from allowing it to breath a little better. I did say probably....
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Old 02-28-2008, 02:46 PM
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Or your dreammeter is not accurate
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Old 02-28-2008, 02:53 PM
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I have personally seen several boats pick up anywhere from 3-5mph with CMIs on HOs. I think a twin 496 cat picked up 9mph. One that comes to mind was a 26 Eliminator V that picked up 5mph and a prop size. Chances are you're going to pick up several mph and a really nice exhaust sound.
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Old 02-28-2008, 07:30 PM
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That was with a GPS
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