When we created this video, we ran the 496 mag, then the 496 ho, and once we finished with those two motors, we put the mag back on the dyno and installed a Raylar 103 kit. His discussion in the video was after we dyno'd the Raylar converted Mag engine with the Dana headers installed.

All of the dyno sheets and tecnical data can be viewd at www.danamarineproducts.com in the instructions area.

We occupied that dyno facility for a week, where Ray was cool enough to give up his time at no charge to work on this project.

As far as results in a boat, we've seen countlesss results due to variables in the boat tiself. We can guarantee the HP increase, but there is no guarantee on how your boat will react.

Smaller, lighter weight boats are going to have a much more positive reaction to 40 HP compared to a single engine 28 foot heavy boat. It's basic power-to-weight ratio. We've had boats pick up 2 MPH to 6 MPH. There is no exact formula, there's alot of variables. Even with the same model boat from two different customers, change the x-dimension, propeller, trim tab placement, etc and your're gonna have mixed results.

Just an FYI: thirdchildhood has a 22 Donzi. Not sure how much lighter and smaller it gets and a proven platform (with standard BBC) for performance increases with exhaust (I'm referring to an article in Powerboat? a number of years back that tested a 22 Donzi with Stainless Marine exhaust and showed real world numbers).

Regardless of all that... at the end of the day the worst power investment to make is exhaust on a stock engine. You can spend thousands on something that will actually make a difference in speed or try the 'pipe' dream and go with exhaust.

I stand by my statement that expensive exhaust upgrades on an otherwise stock 496 or 496 HO is money thrown away. Buyer beware of these 2-6 mph increase claims. They probably come from other changes made at the same time. I SAW NOTHING FROM CMI SPORTTUBES ON MY LITTLE LIGHTWEIGHT DONZI! Here are before and after pics. The cost of that exhaust would have gone a long way toward offsetting the cost of the 525 but I fell for the power and speed increase claims :(. Vette, your post went up the same time mine did. Thanks for validating what I found out the hard way.
http://i763.photobucket.com/albums/x...c007Medium.jpg
http://i763.photobucket.com/albums/x...s096Medium.jpg

I didnt know you could use Captains Call on 525's.

That is a nice benefit.

Yes but the service manual says only use the quiet mode below 2,500 rpms. It is nice to have when idling through marinas and harbors that don't appreciate the sound of an unmuffled 525! Also handy when trying to talk to someone. It also provides a little peace of mind that any water that might get past the internal tip flaps will run down the y (z actually) pipes instead of making it over the hump and into the engine. It was expensive to keep the Q&Q but worth it.

Bigger and Badder
 

Pismo10, no one is limited absolutely to a 4.300" bore who now has a 496 but it requires using a different block like the replacement block we can now use from Dart. The issues with going up to this block is the added cost of the new block and the added costs of addtional accessory and system modifications and upgrades that must be incorporated with a big inch block change due to the new block versus stock 496 block acessory mounting changes.
We have two of these new 600 cubic base engines built on Dart blocks in our inventory now so if any Merc 496 owner is looking for 700HP and north we've got them ready for any owner who is ready to take the 700HP+ plunge with their 496 powered boat! We even designed and built a new intake manifold system that is a step up from our Raylar 496 kit manifold and bigger valve CNC'd Raylar aluminum heads with bigger flow numbers to feed these new monsters with the necessary air flow. If you've "Got the Dime Raylar has the Time" and the products to make a Merc 496 roar!

Best Regards,
Ray @ Raylar

Thirdchildhood, sorry to here about your experience with the CMI headers. I on the other hand have experienced just the opposite. I have the Danas installed on my completely stock 454 mag mpi in a 21’ Hallett and noticed an immediate improvement. Acceleration improved dramatically as well as all around performance. Gained 2mph on top and the sound is awesome. I couldn’t be happier. I agree with Recycle Perf. Many variables and each boat will react differently. I realize were not talking apples for apples here, yours being 496 and mine 454, but my point is, additional power can be obtained by simply bolting on a quality exhaust system.

Here is my exhaust on the “old black engine” as referred to by someone earlier on this thread. Yes, it may be old, but at least mine came with the factory forged rotating assembly. I can upgrade without worries and that includes adding a blower.

http://i806.photobucket.com/albums/y...aExhaust1a.jpg

http://i806.photobucket.com/albums/y...aExhaust2a.jpg

http://i806.photobucket.com/albums/y...aExhaust3a.jpg