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?

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!

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.

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.

i'd only upgrade an exhaust if the current one was shot.

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....

Or your dreammeter is not accurate

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.

That was with a GPS