CMIs on 496 HO-Myth or Real?

[CRC]

Speed increase claims that is. I have seen claims from retailers in Powerboat mag that a swap to CMIs will get you anywhere from 2 to 7 mph. The latest claim being in the Feb '10 issue stating that the owner of a 26 Baja Outlaw can expect 4-7 mph with just the headers and a prop change. That is not going to happen! I fell for this ploy and dropped $4,600 for a set of CMIs to put on my 496 HO in my 2005 Donzi 22 Classic. I saw ZERO top speed increase! I have seen dyno results on paper but I have also seen others post that they too saw NO speed increase. Maybe we can get folks who upgraded their 496 HOs w/CMIs to post their actual results (or lack of results).
Remember, actual results, not paper results.

[Wardey]

The HP is true.....I know the guy that did the test for CMI. Speed is a determining factor. You can dump all the HP in the World to your boat but if it is not set up correctly you will see no terrific gains in MPH.

[HaxbySpeed]

I did the sport tubes and a k&n on a customers 496HO in a 22Donz and picked up 2-3mph..

[MOBILEMERCMAN]

Some boats don't respond to increases in power as much as others. Generally the boats with the drives in the basement respond less. Boats set up with less drag { higher drive heights } are the ones with the notable increases IMO.

[CRC]

The HP is true.....I know the guy that did the test for CMI. Speed is a determining factor. You can dump all the HP in the World to your boat but if it is not set up correctly you will see no terrific gains in MPH.

Wardey, my boat was/is set up correctly. My engine had the all aluminum exhaust which flows really well. I just don't think the CMIs really do much on an otherwise stock 496. It was almost 5k down the drain for me and I cringe every time I see these claims because that Baja owner will NOT see 4-7 more mph from headers and a prop! Now the switch to the 525 which added 100 hp gave me over 10 mph.

Mobilemercman, I already had the Imco shorty on the boat.

[Pismo10]

90% marketing.

[Ratickle]

Speed increase claims that is. I have seen claims from retailers in Powerboat mag that a swap to CMIs will get you anywhere from 2 to 7 mph. The latest claim being in the Feb '10 issue stating that the owner of a 26 Baja Outlaw can expect 4-7 mph with just the headers and a prop change. That is not going to happen! I fell for this ploy and dropped $4,600 for a set of CMIs to put on my 496 HO in my 2005 Donzi 22 Classic. I saw ZERO top speed increase! I have seen dyno results on paper but I have also seen others post that they too saw NO speed increase. Maybe we can get folks who upgraded their 496 HOs w/CMIs to post their actual results (or lack of results).
Remember, actual results, not paper results.

Teague wrote it. Send him an email asking the same questions. I don't know of anytime they've made claims of something they did not have first-hand knowledge of.

[MILD THUNDER]

From some things i have read, the stock merc 496 aluminum exhaust flowed pretty good for a stock merc setup. Way better than the cast iron stuff from the 80's and 90's. Im sure their are some gains to be had, but not enough to see dramatic speed increases on a 496 HO just by bolting some headers on.

Now, if you were to run a stock merc manifold on say a 525, or 600, you would see a huge improvement because the bigger HP engines with with more aggressive cams, heads, etc can move more air thru.

Its like my buddies old 454's. They started out as 370HP mercs. Then they upgraded to larger cams, roller rockers, bumped compression, but left stock cast iron manifolds on. I keep telling him his next best bet would be upgrading exhaust. In his case, upgrading cams and other internal mods should be complimented by adding a free flowing exhaust.

[CRC]

Teague wrote it. Send him an email asking the same questions. I don't know of anytime they've made claims of something they did not have first-hand knowledge of.
I did that a while back and didn't get an answer. I respect Bob Teague and won't bother him any more.

[Raylar]

Bob Teague is CMI's biggest dealer, what the hell you think he is going to say!
As for 4-7 mph in a Baja with CMI's on a stock 496HO, NO WAY!
I've dynoed almost every header made on stock and our Raylar built 496's and I can tell you unequivocally that CMI Sport tubes make between 35-40HP more on a stock 496 than the stock Mercury 496 exhaust and the new CMI Sport tubes do about 20-25HP.
I know about that 50-60Hp dyno test originally done by CMI and I've never seen anybody in the industry re-create that result on a calibrated dyno, running the SAE standard with full accessories and water in the exhaust! You can confirm this with Bob at Full Throttle, he's also done a lot of header dyno testing and the results we have both seen in boats and on the dyno are about the same and pretty consistant. Bob, will also confirm with his propshaft dyno that water in the headers takes away about 15-20HP all by itself as we have seen in wet tests.
As Mild thunder has said if we were comparing Merc's older MPI and log manifolds the increase would be larger and when you go up to 500HP plus on the 496's you also se a slightly bigger increase in power, about 10-15HP more due to the better breathing required. Lets face it there are no realy cheap 40-100HP increase upgrades for any bbc engine especially the 496 family. We oughta know, we've only done hundreds of them!

Best Regards,
Ray @ Raylar

[jet]

how's the old saying go ....THERE"S NO FREE LUNCH

[Ratickle]

As for 4-7 mph in a Baja with CMI's on a stock 496HO, NO WAY!

I've dynoed almost every header made on stock and our Raylar built 496's and I can tell you unequivocally that CMI Sport tubes make between 35-40HP more on a stock 496 than the stock Mercury 496 exhaust and the new CMI Sport tubes do about 20-25HP.


Hey Ray,

What would you expect to see speed increase wise on that Baja with 35-40 HP more like your tests showed?

And what else would you think you'd have to change to get the 60HP they discussed?

[Ted]

Ray, from your tests, do you recall the torque numbers from the different headers? Do they change significantly, or at all? Because, as you know, a header is designed to get more flow which equals in most cases less backpressure. And some engines need backpressure to develop torque, so headers can cause you to lose torque. Which could slow down a boat or at least keep it the same, all other things being equal.

[CRC]

Ray, I always appreciate your input. I'm aware of the CMI hp results on paper. If I had added 35-40 hp to my otherwise stock 496 HO I think I should have seen a gain in top speed. I didn't. When I search this topic on other forums I find others who also saw no noticable increase in hp. Some people report an increase of 1 or 2 mph. Yes, it is Bob Teague making the claims and, yes, he sells CMIs. Like I said, I respect Bob and will continue to do business with his company but I don't like the way he is pushing the CMI Sport Tube headers with these outrageous claims. Now I wonder if these letters are entirely made up? The latest Teague On Tech letter writer is the owner of a 2009 Baja 26 Outlaw, 496 HO, Bravo One, 26p 4-blade. He is asking about "bolt-on power upgrades" for "more on the top-end". Bob Teague replies: "We have found that the CMI 496 Sport Tubes provide the greatest power increase of all the bolt-on exhaust systems. All things being equal, I would expect a 4-7 mph increase in top speed for your boat with this upgrade. You may have to go up a pitch in propeller.....".

My boat responded well to the Imco shorty, BBlades Bravo1 and, of course, the new 525! The headers did nothing to my boat except bling up the engine room. I took a big loss when I sold the 496 with the CMIs.

I'm just wondering what others opinions and real life experiences are on this. Dyno charts be damned!

Ted, good point. A loss of torque could off-set the hp increase and CMI pushers would not be too quick to report a loss of torque!

[Madpoodle]

A WIDE variety of boats here in SoFla will dispute the CMI claims..

They are damn purty though, but chrome don't get you home..

[Ratickle]

They are damn purty though, but chrome don't get you home..

Now you tell me......:eek:

[Biggus]

From my own experience, to gain speed on a straight bottom single engine boat it takes 20 hp/mph. It would most likely take a 140 hp increase to gain the 7 mph claimed.

[GB]

90% marketing.

Yeap, 90% ++++++

[JupiterSunsation]

Some boats don't respond to increases in power as much as others. Generally the boats with the drives in the basement respond less. Boats set up with less drag { higher drive heights } are the ones with the notable increases IMO.

I know a guy that had a 288 Sunsation and got 1 mph increase but then was selling the boat, took off the exhaust and still had the 1 mph.....go figure :confused:

[CRC]

From my own experience, to gain speed on a straight bottom single engine boat it takes 20 hp/mph. It would most likely take a 140 hp increase to gain the 7 mph claimed.

OK so I'm not the only one disapointed in the CMIs. Funny how adding only " 100 hp" with the 525 gave me a solid 10 mph increase from about 75+ to 85+. Maybe they are sandbagging on the rating!

[MOBILEMERCMAN]

I know a guy that had a 288 Sunsation and got 1 mph increase but then was selling the boat, took off the exhaust and still had the 1 mph.....go figure :confused:

A couple hundred hours will loosen the drive and may be the 1 mph he noticed.

[DAREDEVIL]

I think this is like everything else.......

the parts and boat and prop need to match 100% then u may see a gain in a better exhaust ?!

If nothing really is dialed in u won't see a differents in just changing headers exept for maybe sound. LOL:rolleyes:

[CRC]

I think this is like everything else.......

the parts and boat and prop need to match 100% then u may see a gain in a better exhaust ?!

If nothing really is dialed in u won't see a differents in just changing headers exept for maybe sound. LOL:rolleyes:

I really don't think that the stock 425 hp 496 needs the extra breathing capability. Mine had the aluminum exhaust and the ports were huge. I really wanted to tell myself that after spending almost 5 big ones and doing all that work that there was some improvement but that fact is, there wasn't. My advice is to save the money unless you are redoing the complete motor or have an extra 5 grand laying around to blow on bling. To keep publishing these claims of 4-7 mph on a single engine boat just to sell more headers is not cool.

[DAREDEVIL]

My advice is to save the money unless you are redoing the complete motor or have an extra 5 grand laying around to blow on bling. To keep publishing these claims of 4-7 mph on a single engine boat just to sell more headers is not cool.

:iagree:

[Wardey]

Bob Teague is CMI's biggest dealer, what the hell you think he is going to say!
As for 4-7 mph in a Baja with CMI's on a stock 496HO, NO WAY!
I've dynoed almost every header made on stock and our Raylar built 496's and I can tell you unequivocally that CMI Sport tubes make between 35-40HP more on a stock 496 than the stock Mercury 496 exhaust and the new CMI Sport tubes do about 20-25HP.
I know about that 50-60Hp dyno test originally done by CMI and I've never seen anybody in the industry re-create that result on a calibrated dyno, running the SAE standard with full accessories and water in the exhaust! You can confirm this with Bob at Full Throttle, he's also done a lot of header dyno testing and the results we have both seen in boats and on the dyno are about the same and pretty consistant. Bob, will also confirm with his propshaft dyno that water in the headers takes away about 15-20HP all by itself as we have seen in wet tests.
As Mild thunder has said if we were comparing Merc's older MPI and log manifolds the increase would be larger and when you go up to 500HP plus on the 496's you also se a slightly bigger increase in power, about 10-15HP more due to the better breathing required. Lets face it there are no realy cheap 40-100HP increase upgrades for any bbc engine especially the 496 family. We oughta know, we've only done hundreds of them!

Best Regards,
Ray @ Raylar

Hmmmmm....Guess those were bogus dyno sheets I was looking at ???? They DO create almost 60 HP on the sheets I saw. If I remember it was 57. On a second note, put the riser off your stock 496 risers and look at the anti-reversion ring inside. With this ring your exhaust is restricked to about 2 " in diameter.......pull the rings out for the price of a gasket set and you will see good gains but forget about your warranty after.

[Pismo10]

Hmmmmm....Guess those were bogus dyno sheets I was looking at ???? They DO create almost 60 HP on the sheets I saw. If I remember it was 57. On a second note, put the riser off your stock 496 risers and look at the anti-reversion ring inside. With this ring your exhaust is restricked to about 2 " in diameter.......pull the rings out for the price of a gasket set and you will see good gains but forget about your warranty after.

Not real world wet prop hp results like Ray said before. I think CRC had switchable exhaust as well which would also hurt any gains. I dont know to. Did you keep the switch exhaust after the CMI were installed?

35-40hp in a Donzi 22 classic should have given you a noticeable top end increase.

CRC, I also think your move the the 525 was probably more like 130+hp increase at the prop. Those 525s are nice.

[jrz]

Since all of the dyno results are faked, call Teaque for real world "non dyno" boat results.

[Raylar]

I am not saying any dyno results were faked here! As many of you know, there are different ways to set up a dyno calibration on any given run and also depends on how the engine is equipped on the dyno, when was the last time the dyno was calibrated, etc.,etc. We tried very hard to use SAE standards on our dyno tests, a properly calibrated and tested dyno and running the headers wet for real world results. How others ran their dyno tests on what in testing the CMI's with those dyno runs, I don't really know or care. What really counts is how the various boats and engines respond in the boats and under real world results in a lot of real world boats the results were for the most part as follows: 1. no change in performance. 2. 1-3 mph increase in performance. 3. A nice cool idle sound and lots of bling.
These are the results that really count, everything else is just talk and dyno numbers! You can take that to the bank baby!

Best Regards,
Ray @ Raylar

[Ratickle]

I would think the 35 - 40 hp you got with the CMI's only would be a pretty decent gain. I certainly would not be pizzed seeing a number like that.

[HaxbySpeed]

For the $ on a 496HO I don't think it's worth it. IMO. When I did a set of sport tubes for a customer a few years back they were around 5k with the quick and quiet tails. That was just the initial cost.. Doing the re&re in a 22 classic is a bit of a b!tch. Also the fitment wasn't great and you lose the ability to pressurize and drain the raw water. They're heavier then the stock manifolds as well. With the headers, labbed prop, and K&N we picked up 2-3 mph. It's hard to say what the exhaust alone did, I should have tried a back to back test. On an older Z25 with an HO I removed the turbulators, spent an hour or so porting the stock exhaust where it merges at the riser, and had the rev limit raised. It picked up 1.5mph for a fraction of the cost. The CMI's do look nice though, and sound better too.. I guess it all depends on your budget.. :cheers2:

[jrz]

I am not saying any dyno results were faked here! As many of you know, there are different ways to set up a dyno calibration on any given run and also depends on how the engine is equipped on the dyno, when was the last time the dyno was calibrated, etc.,etc. We tried very hard to use SAE standards on our dyno tests, a properly calibrated and tested dyno and running the headers wet for real world results. How others ran their dyno tests on what in testing the CMI's with those dyno runs, I don't really know or care. What really counts is how the various boats and engines respond in the boats and under real world results in a lot of real world boats the results were for the most part as follows: 1. no change in performance. 2. 1-3 mph increase in performance. 3. A nice cool idle sound and lots of bling.
These are the results that really count, everything else is just talk and dyno numbers! You can take that to the bank baby!

Best Regards,
Ray @ Raylar

All of the major marine engine manufacturers testing of the 8.1's, along with the development of the GM HP3 496 were done on uncalibrated dynos?

[PARADOX]

Dyno / lab condition is just that. "Maximum" possibility within controled environment. Just like Ray was stating. As far as ANY CMI systtem... run like hell. Sooner or later, you will be buying a new motor.
However there is a nother way to look at the so called HP gain issue. Any given motor, let's say 496 or a 502 will put out "X" amount of HP. Unless it's blown, but from a 502 block the max theoretical HP you can get is (I assume) +- 1000HP. not you start "loosing" HP with all the moving parts. So I don't think it's how much HP an engine is gaining.. it's more like how much HP you'r not loosing.
Power steering pump, oil pump, fuel pump, alternator, rocker arm/lifter movement, rotating counterwieghts, pushing out exhaust. etc. Now you'r down to 1000 HP minus all HP lost to the motor actually running and working.
So.. the least HP you loose, the more HP you have for the props. I don't think HP can be "added" (again, unless it's blown or something) it's how little HP you loose adding High Perf. parts. You can't get a V-8 to get you a V-10 performance with all things being equal. No HP gain.. less existing HP lose is the name of the game. In my .02

[CRC]

Pismo, yes I have Q&Q which I only use at idle or minimum planing speed now. I also had it to begin with so I don't think that it would negate any power gain. Ray, your input is always appreciated. I never said that the dyno sheets were fudged; Just wondering where all that extra hp was?:confused: As much as I wanted to say that I gained something the fact is that it did nothing for my boat's top end. I changed nothing else when I did the headers and I saw no gain.:confused:

[Wayne Pennell]

CRC; I have debated this on forum's and in my head over and over. My finding are exactly what you say....no real world gains. In my mind, the ONLY way one could gain MPH is by being on the very edge of a prop selection...say running a 24P at 5050 RPM and doing 65 MPH. Now adding the CMI's net you a few RPM's and now you have to run a taller prop i.e 26P and can turn that at 4900 or 4950 at 67 MPH. That would be the only way I could see to gain anything. I have chosen to go a different direction with gain with an extension box.

Nice thread

[CRC]

CRC; I have debated this on forum's and in my head over and over. My finding are exactly what you say....no real world gains. In my mind, the ONLY way one could gain MPH is by being on the very edge of a prop selection...say running a 24P at 5050 RPM and doing 65 MPH. Now adding the CMI's net you a few RPM's and now you have to run a taller prop i.e 26P and can turn that at 4900 or 4950 at 67 MPH. That would be the only way I could see to gain anything. I have chosen to go a different direction with gain with an extension box.

Nice thread

Thanks. I chose a different direction too...:sifone:
http://www.youtube.com/watch?v=i7H6zNFH8f0

[Raylar]

I guess I am always amazed how sometimes the stock 496HO 425 gets compared to a Mercury Racing HP525EFI. Heck, that comparison is really an apples and oranges comparison.
First the HP525EFi is 540HP right outta the crate, thats 115 more than the stock 496HO. Yah it should make more power and speed it has more. Its also a hell of a lot more expensive, ie the apples and oranges comparison!

Just some food for thought here. Raylar took two absolutly stock 496 MAGS !! for Sunsation, $5K less than 496HO, equipped them with the Raylar HO525 standard off the shelf kits and stock exhausts and reprogrammed the ECM's and put some nice bling on the engines with powder coating and relocation kits. Sunsation installed them into a 32 SSR (awesome boat!)Sunsation with standard BRAVO 1X drives and Hawkeye took the boat to LOTO last year and ran 96 MPH. Just a mile or two faster than the same boat with HP525EFI's with Bravo XR Sportmasters. How did that happen, well its because the 496's properly upgraded will run with or outrun most HP525EFI's especially when equipped with a good set of headers like the HP525EFI.

Don't believe me, call Joe at Sunsation or the guys a Hawkeye Boat Sales and they will confirm along with all the other observers at the Loto Shootout!
Whats the point, a customers wallet will have a fatter side view due to the extra cash still in there! About $40-50K on the average twin engine boat!
If that cash ain't important to Ya, Could I please get you to put in in a plain envelope and donate it to the Raylar needs capital Foundation, we accept all chartible contributions!
GET your 496 up to comparable numbers, then lets make the comparison!

Best Regards,
Ray @ Raylar

[jrz]

[QUOTE=Raylar;419482]I guess I am always amazed how sometimes the stock 496HO 425 gets compared to a Mercury Racing HP525EFI. Heck, that comparison is really an apples and oranges comparison.


The comparison is to a GM HP3 8.1 engine, not the 525, I know the difference.

[CRC]

I'm not comparing the 496 to the 525. It's just the route that I chose to go after talking to a lot of folks. I found a vintage 2007 motor with 30 hours for 20 grand. That's all I'll say here since my intention in starting this thread was not to compare engines but to discuss the claimed power gains from CMI headers on the 496.

[Wayne Pennell]

Just some food for thought here. Raylar took two absolutly stock 496 MAGS !! for Sunsation, $5K less than 496HO, equipped them with the Raylar HO525 standard off the shelf kits


I am not wanting to do the entire kit just yet, is it worth just a Raylar cam change for starters?

[jrz]

Page 8 of our catalog at www.custommarine.com shows four of the many results responces from customers. Teaque also ran 4 or 5 quantified before and after header installation tests with great results, you can call him at 661/295-7000. I myself have no need to make up data, after 100's of 496 header installations and 25 years of this job, it would not be worth it.

[CRC]

Page 8 of our catalog at www.custommarine.com shows four of the many results responces from customers. Teaque also ran 4 or 5 quantified before and after header installation tests with great results, you can call him at 661/295-7000. I myself have no need to make up data, after 100's of 496 header installations and 25 years of this job, it would not be worth it.

Would you include myself and others who saw NO gain on page 8 of your catalog?;)

[Pismo10]

What is a guy from TCM going to say..Come on..

[Raylar]

Jrz:

Lets not get your panties in wad here!
I am not saying anyones dyno pulls were fudged, tweaked or otherwise. Two different dynos will usually have some differential as well as the other factors affecting a dyno pull on an engine like, coolant temperatures, time sweep of actual dyno pull, fuel type used, etc.,etc.
What is important to remember here also is that actual power made on an engine upgrade does not always translate directly to speed increases in various boats. There are too many other factors that will affect speed in any given boat, like weights , hull design, drive mounting height, type of water and air temperatures, altitude, hooks in hull, driver skill, etc.,etc., etc.
What these paticular boaters are referencing here is that on their own boat, same boat, same drive, same boating location, same driver, roughly the same boating conditions they saw absolutly little or no measurable increase in the speed and performance of their boats. We would also like to believe that if their original prop pitch was not changed that their top rpm should increase lets say 200-300 rpm and they should be able to use a larger pitch prop of same type and style and see a corresponding speed increase.
If one was to make a simple assumption from this input one would assume that if the CMI Sporttubes made 50-60HP as your dyno charts and dealers advertized, that a 50-60 HP increase in engine power which would be about 13-15% increase in engine power that this should translate to some performance increase.
I guess this is a case of 2+2 not equaling 4 and thats what has got them asking questions and feeling shorted since as bang for the buck goes, their
$4K to $5K investment appears to have yielded no real increase which makes the investment pretty hard to justify for them.
I know as well as others who have tested various true header systems versus stock and aftermarket manifold systems that true headers such as the CMI sportubes, Dana Flo-torque, Kieth Eikert cast headers, Hardin Marine headers and Lightning headers make measurable power increases. Our testing as well as Bob at Full Throttle and some others has shown time and time again that generally these increases on stock 496MAGs and 496MAG-HO's ranged between 30-45HP. Even at these modest level increases most hulls should respond to this power increase with a 1-2 mph increase @ about 15-20HP needed per mile per hour. In many cases this did happen and was documented by many boaters with before and after in the water testing.
The problem that exists now is that with the claims of 50-60HP for CMI Sporttubes over stock exhaust that it seems even less likely that a dealer should claim that a particular boat increased its speed by 7 mph with no other changes. Either that boat in question had some other issues, like a bad prop selection to begin with which was corrected after installing and testing the new header system, other upgrades were made at the same time, a new an more expierenced driver did the after testing who new better how to trim and run the boat, conditions before and after the change were significantly different or something along these lines.
In any event lets always be careful to make the testing somewhat scientific to properly document before and afters and if your 496 sportube headers make 10-20HP more than some of these others lets see it really demonstrated in a single boat, on the water, same test, same conditions and equipment and it should be demonstratable that CMI's can generate 7mph more speed than stock exhaust, especially when compared to other headers.
I know where my money and bet will be!

As for the HP3 496 -525HP program your making a non-conforming comparison since the GM Vortec HP3 engines that were built and run by Innovation were never tested with any form of stock exhaust, since GM does not make marine exhaust and the engines were not available with any other exhaust than the CMI headers your company originally provided for the GM program.
And when it comes to 496's I don't think there are too many people in our industry with more knowledge or expierence with hundreds of 496's that we have here at Raylar.
As I keep telling and proving to everyone in the industry, the newer Mercury Marine exhaust manifolds and risers as designed and built for the 496 engines are a really big improvemnt over older designs and types used on the 454-502 mpi-efi engines and are still an equal to the Gil type systems that Mercury installed on the HP500 engines.
I know your dealers want to sell your headers and systems and make a profit for themselves and you just as anybody who is in this business does.
I just think its about time this industry in general starts making more factual based claims and stop using adjectives like as much as, up to, etc. etc.
Every good manufacturer,distributor and vendor should be prepared to back up his claims and advertising with real world results and proven results.
If the results are less than advertised, the advertising should be modified to fit the actual results.
When performance boaters buy expensive equipment like headers, engines, drives, upgrade kits and such they should be delivered a product that meets its claims, no more no less!
In other words you get what you paid for!

This is where the integrity and future of our sport and business should be demonstrated and protected.

Best Regards,
Ray @ Raylar

[CRC]

I didn't want to quote all that but great post Ray. That about says it all and from a guy who probably knows more about the 496 than anyone else! The Donzi 22 Classic responds well to power increases BTW.

[launchpad]

how fast is that classic now, just out of curiousity?

[Donskihp]

I installed the CNI 496 sport Tubes on my 496HO in 2007. Prior to the installation I was running 68mph in my 2005 Donzi 26zx. I was not hitting the relimiter at that time. After the installation I was hitting the relimiter so I steped up from a Brovo 1- 24p to a 26p. I gained 1.4 mph.( Speed went up to 69.4mph) I would have gained more speed if I hadn't also gained slippage. I went from 10% slip to 16%. The 26zx has a very high X dimension,wich I later discovered and found the Brovo 1 was adding to my transome lift ,increasing my slippage. Any way I realized a speed gain with the CMI's. But if you really want to gain speed the Whipple supercharger will do a fine job. I read an articled on horse power vrs/speed and how much hp it takes to gain 1 mph,the the test said it took 20hp to gain 1 mph. That seems to be about right for my experance.

[gcarter]

So while this is still going on, what would be the best way to spend $5K on a 496, or a 502 for that matter?
I know CRC, and I tried to discourage him from going the route he went. I suspected the results he got were what would happen.

So, back to my question.....how could $5K be better spent for better results?

[Donskihp]

For 5k you could proCharge a 496 and Whipple is about 8k. However any one supper Charging a 496 needs to know if their 496 has forged internals. It won't hold up if not forged.

[blackhawk]

The latest claim being in the Feb '10 issue stating that the owner of a 26 Baja Outlaw can expect 4-7 mph with just the headers and a prop change.

Actually I believe that. CMIs were probably good for .5mph and the prop was good for 3.5-6.5 mph. :willy_nilly:

[ElvisAaron]

good tips, thx a lot
__________________________________________________
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[Gordo]

Since this has become an Exhaust manifold/header discussion, Is there ANY difference between the CMI and the Lightning Headers? and
What (if any) difference between the tube primary headers and the cast headers, such as RM, Stainless Marine, Dana, etc..
I can start another thread if y'all want...

[Wardey]

Since this has become an Exhaust manifold/header discussion, Is there ANY difference between the CMI and the Lightning Headers? and
What (if any) difference between the tube primary headers and the cast headers, such as RM, Stainless Marine, Dana, etc..
I can start another thread if y'all want...

Hey Buddy, Give me a shout.

[FTMBOB]

I've dyno'd 496's back to back with stock, Dana and Lightnings. Here's a link to my web site where I posted the results. http://fullthrottlemarine.com/496%20Mag%20Dyno%20Article.htm I also tested the CMI sport tubes before & after on a 496 HO at the prop. The CMI's gained 28 HP over stock. The Dana's
gained 23 if I remember correctly and the Lightnings a couple less than the Dana's. Bang for the buck I'd go with Dana's.

Bob



Since this has become an Exhaust manifold/header discussion, Is there ANY difference between the CMI and the Lightning Headers? and
What (if any) difference between the tube primary headers and the cast headers, such as RM, Stainless Marine, Dana, etc..
I can start another thread if y'all want...

[Gordo]

On the typical twin engine boat, how much weight savings between the old stock factory cast iron exhaust, and the tube headers or the custom aluminum headers?