How much money are you actually willing / capable of spending on the engine? Figure out a REAL number of dollars and everyone can give you realistic guidance including me. I have been through three incremental upgrades starting with a stock 496HO and have made of plenty of expensive mistakes along the way. I have lessons I would be glad to share. Give a $ number so everyone can focus on what makes sense. The Velocity hull has a big pad that responds well to + hp.

Stainless Marine

Dig deeper. Check under the sofa cushions....:signs069:

[YOUTUBE]http://www.youtube.com/watch?v=cNsH6FUaElQ&feature=related[/YOUTUBE]
Maybe I should stick it out another year...
I think I need a bigger, faster boat...

But $2000 is all I would be willing to go I can handle the work so just figuring part.. probably better off holding out and upgrading the boat and all....

I don't know what the cam and gasket set would cost and ECU flash. You might be able to do that for around $2,000 and at least get up to a 496 HO. That's if you do it yourself. Speed is expensive. Reliable speed is even more expensive (but cheaper in the long run). I put about 40g into my little Donzi. Combined with the purchase price of 55g that's around $95,000 in a 22' boat. I deserve it though ;). Again, don't waste money on the exhaust. Yours flows plenty good for up to 425 hp.

You don't need a bigger boat. You need bigger power and drive and steering if it isn't full hydraulic.

http://www.offshoreonly.com/forums/s...-seperate.html

:) :) :) :)

I missed your $1000-$2000 avaiulable expenditure estimate on first read. For that, upgrading to the 496HO seems the best bet. That is a cam and ECU upgrade. Look/advertise for a used 496HO cam on OSO or buy new. A new ECU is ~$1500but Dustin Whipple is licensed by Mercury (he is the only one so liscenced) to modify the Mercury PCM555 ECM program. His fee is $800. $400 of that goes to Mercury to unlock your ECU. I do not know for sure since I started with a 496HO but I would think he could reflash your ECU to a 498HO. Call him at Whipple Superchargers.

If you find extra dollars the Dana Flow Torque Exhaust will give you ~2x extra hp with wet exhaust on a 496HO for $2500. Their add says something like 47hp increase on the 496HO but that is with dry exhaust. The CMI Sport Tubes (~$5000) claim like 6x hp increase on the 496HO but that is also with dry exhaust. With wet exhaust the CMI's are only like ~5hp more than the Dana's. Google 'Full Throttle Marine' (Bob Lloyd's web site article 'Myth Busting') for the actual 496HO wet exhaust test data comparison of the Dana Torque Flow vs the CMI Sport Tube exhaust hp.

If you decide to spend more there are obviously other options.

SORRY I ALWAYS WRITE IN CAPS. THANK YOU FOR ALL YOUR INPUT. WELL THE ENGINE WORK WILL HAVE TO WAIT TILL I GET THE BOAT PAID OFF. THE BOAT RUNS GREAT NOW SO I'LL JUST ENJOY IT FOR NOW:)

THEN ADD THE WHIPPLE:)

LOL!!! THAT IS GREAT

Do tell......some of use are currently trying to make more power of these 496's.......any info would be appreciated.

I've got a couple of used HO cams if anyone is interested. If you can do the labor yourself, changing the cam and a Whipple reflash is a lot of bang for the buck. I've done a lot of them, and just about any other 496 mods you can think of. Dart has just released cast iron heads for the 496. Supposed to work really well. Tyler Crocket is testing them now.

Bob Lloyd
Full Throttle Marine

Bob,
How much for an HO cam? Would I have to change rockers, springs, or anything?
Thanks
Joe

Nope,just cam,reuse lifters because their roller lifters,reflash ecu,drill out idle bleed hole from 1/8 to 1/4 at throtle plate and you have a 496 mag HO,done that to my twin engine 30 foot powerquest,went from 73.9 to 80.2 gps speed.best bang for the buck

I'll take $200 for a cam. Just a pcm flash & drill out air bleed hole.

hi all can anyone tell me if my 496 ho would of had the aluminum exhaust the motors are 2001 ,but i only bought it last year and the guy replaced both sets of exhaust the ones on the boat now are iron ,did not buy the boat from owner so i can not ask him bought it from National/L in fl reading the above it sounds like some ex ports are better than others on the 496HO thanks paul

Best place to start is Bob Lloyd's Full Throttle Marine web site http://www.fullthrottlemarine.com/. Go to the "View Our High Performance Projects" and read the "496 Mag Dyno Testing & Myth Busting" article. I addition read the follow up information Bob posted on OSO, post #1 & #4 regarding the CMI Sport Tube headers: http://www.offshoreonly.com/forums/g...dyno-test.html

#1 To get unbiased straight skinny regarding 496 upgrades bang for the buck call Bob Lloyd. He is my go to guy for over six years now. He can give you the answer as to what you need to get the performance you want from the hull you are running and the best package for that. As power goes up additional upgrades in the drive and/or steering can also be necessary. #2 Any custom head or throttle body porting go straight to Jim Valako. #3 Any custom cams go straight to Bob Madera of Marine Kinetics or Raylar cams if you are keeping the stock heads and valve train. #4 Dana Torque Flow exhaust is the best bang for the buck on a 496. #5 If you want 525hp out of a 496 buy the Raylar kit and change to forged pistons.

Where can info on the new 496 Dart heads be found? Price?

On paper they are showing big gains. In real life many of us have seen absolutely no improvement on a 496 Magnum HO. Search it. I'm not the only one. I don't know where they get those numbers. A few people report 1 or 2 mph gain but I bet sometimes it is wishful thinking. Again, research real world results. Not numbers on paper.

This guy claims a 11 mph increase and he did bottom paint at the same time.....bottom paint on a Donzi Ragazza? http://www.offshoreonly.com/forums/1887205-post7.html

Anyone considering exhaust upgrades for the 496 should read this thread, starting with post #9. Save your money for something that will really work... http://www.offshoreonly.com/forums/g...bang-buck.html

Thanks for the info......

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!

Couple questions since i am in the same situation.
#1- what order would you start to do the mods (cam and pcm, then exhaust or the other way around)

#2- would you recommend the raylar 103 cam or the stock 496HO cam ?

Any gains in the stock heads to be had? slight port and polish or is it a total waste of time?

I have a Baja Outlaw 25 with 496 mag and was planning on doing cam and pcm, then headers, then prop work ( I am leaving prop til last due to the variations of altitude that i run on for lakes) Oh and doing work to the bottom side of the boat but thats a whole other post....

Sheldon

i run a 496 HO
took the K&N off and used a larger flame arester
installed CMI ETop Headers
and put a 26 labbed 4Blade prop
went from an average speed of 62 mph
to an average of 68 mph all gps speeds on my laveycraft
also boosted the fuel pressure 5 PSI to maintain air fuel ratio with the extra scavenging of the headers
and im not doing anymore to this motor......
cheaper to buy a whole new hull with the power i want than it is to modify

WOW!!! SO MUCH GREAT INFO IN THIS TOPIC. NO I REALLY DON'T KNOW WHAT TO TRY OR WHERE TO START. BY THE LOOKS OF IT I'M BETTER OFF KEEPING MY MONEY IN MY POCKET AND WAITING TILL I HAVE ENOUGH TO TOTALLY REBUILD MY 496HO AND ADD A WHIPPLE. THANKS AGAIN FOR ALL THE INFO GUYS:)

Curious, what was the first prop and the rpm you ran for the 62 mph and what is the rpm you run at now for the 68 mph?

Yeah, one thing at a time. The flame arrester did nothing unless someone had put a ridiculously small one on there and......6 mph from exhaust upgrade? It's not that easy...............

The K&N just plain sucks - my boat went 1-2 MPH slower.

5PSI? Just for headers? That would drown a 496, does you transom look like a coal mine?

the boat when i bought it was underproped the tack read full rpm but it wasnt a good guage i have since replaced the guage the prop that came with was a 22 bravo 4 blade laveys in my size with a 496 ho come stock with a 24 bravo 4 blade

exhaust , and labbed prop..... the added fuel pressure is only to protect the mixture ratio

it was only the delivery pressure nothing else.... and it does soot up in the early part of the season .....but it beats a roached engine all to hell

now having said all this......... the headers most likely only gave me 20 to 30 more hp perhaps a bit more
this allowed me to spin a larger prop but it need to be labbed.....
my mechanic and i did touch 70 once with a labbed 3 blade
but the overall handling characteristics were horrible
back to the 4 blade.....and the cost averaged out to about $1000 per mph for the purchase and work done