Any Downside to Adding CMI Headers to 496 HO's?
12-25-2006, 11:46 AM
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Any Downside to Adding CMI Headers to 496 HO's?
Greetings all - so, I've only logged 25 hours on my '07 28 daytona, and had to put it away for a long winters nap.
I've been researching what I might be able to do to squeeze a little more speed out of this boat without breaking the bank. I've concluded that CMI Headers and some prop optimization may be the route.
One of the reasons I ended up in the package I did, is I wanted to maximize reliability and didn't want to spend my days wrenching instead of boating.
Will adding these headers decrease my reliability?
Will they invalidate the Merc warranties (motor and drives)?
Is there any downside to these mods?
I am currently maxing out at 100mph - what might I anticipate improving to? (5mph?, more?)
I've been researching what I might be able to do to squeeze a little more speed out of this boat without breaking the bank. I've concluded that CMI Headers and some prop optimization may be the route.
One of the reasons I ended up in the package I did, is I wanted to maximize reliability and didn't want to spend my days wrenching instead of boating.
Will adding these headers decrease my reliability?
Will they invalidate the Merc warranties (motor and drives)?
Is there any downside to these mods?
I am currently maxing out at 100mph - what might I anticipate improving to? (5mph?, more?)
12-25-2006, 12:12 PM
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Re: Any Downside to Adding CMI Headers to 496 HO's?
I've been studying the same issues for my 496HO 30' Daytona.
They will not hurt reliability one bit.
Merc would have to prove the headers caused the problem to deny warranty legally (At least in the states, it's law). This is unlikely. Merc ran the std bravo to 525 hp and XR to 600- You got the X if I remember right- you'll be fine- though I would upgrade to the larger XR lower shaft when you can- 1" shafts are known to fatigue with surfacing props on cats and they will break at the frt of the prop and make a nice fish attractor to go with the new hole in your wallet.
I think 5-7 is there to be had in our boats (posterchild for this mod), will take prop tuning
The downside is you will likely have to remove the engines to get the outbard headers on. a lot of Daytona's with 525's (similar headers) have notched hatches to clear the tubes on the inboard headers- check this out too so there are no surprises. I'm pretty sure you will need custom tailpipes which will enlarge the whole in your wallet.
To be honest, I really like the Bassett Racing headers for the 496. The tri-y design is proven effective, they are more compact for fitting in tight places, more affordable (by a lot) but you'll still need tailpipes and you'll have to fab your own relocation kits for the oil filter and PCM etc.
If/ when you do it, you'll have to tell us all about it
They will not hurt reliability one bit.
Merc would have to prove the headers caused the problem to deny warranty legally (At least in the states, it's law). This is unlikely. Merc ran the std bravo to 525 hp and XR to 600- You got the X if I remember right- you'll be fine- though I would upgrade to the larger XR lower shaft when you can- 1" shafts are known to fatigue with surfacing props on cats and they will break at the frt of the prop and make a nice fish attractor to go with the new hole in your wallet.
I think 5-7 is there to be had in our boats (posterchild for this mod), will take prop tuning
The downside is you will likely have to remove the engines to get the outbard headers on. a lot of Daytona's with 525's (similar headers) have notched hatches to clear the tubes on the inboard headers- check this out too so there are no surprises. I'm pretty sure you will need custom tailpipes which will enlarge the whole in your wallet.
To be honest, I really like the Bassett Racing headers for the 496. The tri-y design is proven effective, they are more compact for fitting in tight places, more affordable (by a lot) but you'll still need tailpipes and you'll have to fab your own relocation kits for the oil filter and PCM etc.
If/ when you do it, you'll have to tell us all about it
