Tyler Crockett I believe.

http://www.crockettmarineengines.com/index.html

Are you saying that you upgraded a 496 Mag (Merc claimed375hp) to a 496 HO (Merc claimed 425hp) and saw no increased performance from your 22 Donzi Classic?

No. I'm saying that I fell for the bullsh*t power and speed gain claims on the CMI Sportube headers and dropped $4,600 for a set. I put them on my otherwise stock 496 HO and saw ZERO speed gain. I am not the only one. I'm looking for the thread now. Remember that Powerboat Mag is in bed with Bob Teague and Teague sells more CMIs than anyone else.....I called him out in a letter to Teague on Tech about it and of course got no reply. Also, Full Throttle sells the exhaust and Raylar kits that they tested. How convenient.

I added some links on post # 59.

I have my own story to rant about being mislead by a Power Boat Mag Test of a Nordic Rage with at 496HO so I can believe what you say regarding that entity and their contributors. I still do love the Rage.

However it is patently unfair to mention Full Throttle Marine in that context. Most glaring is the fact that Full Throttle Marine actually dyno tested (at their own expense) the 496HO with the CMI Sport Tube Headers versus the stock 496HO exhaust and reported on OSO that the CMI's ONLY MADE 24hp more than the stock exhaust when running wet exhaust versus the CMI advertisements claiming like ~67hp (from dry exhaust testing)
http://www.offshoreonly.com/forums/g...dyno-test.html
24hp can be good for ~1+ mph on a high performance hull. The Donzi Classic hull is a traditional off shore deep V that may not be that responsive to a 24hp increase. Just a thought.

Regarding this item you posted related to the false exhaust claims http://www.offshoreonly.com/forums/1887205-post7.html the guy says he did three things ie added CMI's, bottom paint but also a prop change which you did not mention. Depending how badly he was previously propped he may well have gained 11 mph as he claimed but no way from only the CMI's and/or the bottom paint. Still that 11 mph gain is extremely hard to believe.

Fair Comparrison
 

You gotta remember that adding that 50HP to two different boats will usually or always net different results.

To be clear about what I said earlier regarding the computer re-programming...

If you are uploading the 425 program into a 375 box, then yes some people will see gains.

My point is that if you already have the 425 and if you think you can change that program (only) to go faster... No.

That engine does not "like" very much additional advance. It won't run any faster - just leaner

If you raise the rev limiter and prop it up without changing any parts then you have effectively shortened the life if you do much wot running.

Bob Loyd's a good man. For what my little opinion is worth, I trust him and I'd not hesitate to do business with him.

Full Throttle Info In Post #63
 

I don't believe it is fair OR ACCURATE to tie Full Throttle into the negative connotation regarding the simple fact that they sell parts that did not satisfy some boat owner.

The endless number of variables surrounding any installation or upgrade are to vast to simply throw them in like that.

I can pretty much promise you that if you take your whole rig to Bob and let him take care of it, you will be satisfied.

If you buy parts from him and do your own thing or some conglomeration of ideas then he would merely be the "guy who sold you parts"; NOT a guy who cheated you or provided you with incorrect information that failed to net you some increase.

I respect Bob Teague but he continuously publishes claims of speed increases of 2-6 mph simply by bolting on CMI Sportubes in his Teague On Tech column. Many of us in the real world see nothing!

I linked the Regazza story because I stumbled on it while looking for the other thread and thought it was funny.

I have no bone to pick with Full Throttle but why are these hp increases showing up on paper but not on the water?

The ports in my stock aluminum 496 manifolds were huge and certainly not restrictive. Headers should scavenge better but apparently it makes little or no difference on an otherwise stock 496.

I'm just trying to give a heads up here to do some real world research and talk to other boaters who have no conflict of interest before investing heavily in exhaust for a 496.

That's ok Teague also still says that synthetic oil is too slippery.. :grinser010:

It's the boat. Adding power to any boat just does not equate to performance increases across the board.

You have to "know" or "experiment" with how your particular boat responds to power upgrades.

For instance, an average Bayliner, Sea-Ray, Maxum, family-type boat has no real ability to lift and carry the bow. It was never meant to do that. Even Donzi has boats that are designed like or similar to the brands I mentioned above. Ever seen the Donzi small cabin cruisers?

If you can't reduce the wetted surface of the boat, then additional power will not be as noticeable or in many cases won't be noticeable at all.

You must have something decent to start out with regarding the bottom, X-Dimension, etc.

I get it. A lot of claims out there are or can me misleading. What you have to know is that "someone, somewhere" got those numbers so they post it and sell it.

Marketing! :drink:

Ha, now full synthetic oil is good since he is sponsored by Amsoil.

Conflict of interest

And horsepower is horsepower and the Donzi Classic responds well to it! Going from the 496 HO to a 525 got me 9-10 mph!