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DudeHoss
06-05-2006, 08:52 PM
Hello Fellow Donzi Enthusiasts! This is one of many dumb questions to come from a new Donzi 22 Classic Owner. I just bought a 1997 Donzi Classic with about 140 hours on it. It has the 454 Magnum in it with Corsa Silent Choice Exhaust. As far as I can tell it puts out 385 Php. (There is nothing more dependable than stock) What are the first few cost effective engine mods you would make to get some better performance from this engine? Then I will experiment with some props. Dwight has helped me with a few engine dress up ideas but I want to know what HP other are getting form there 454 Magnums’s. I’m not looking to go all out but I would like over 400+ Php and 70mph on the water. Any suggestions would be greatly appreciated. Thank you for your advice on the question about “Sanding out the Hook on a 22 Classic.” I will tackle that project this October. Thank you again Dwight for all of your help.

MOP
06-05-2006, 09:11 PM
First thing I would do is to ditch is the stock iron exhaust, let it breath a little better. You can find some very good deals on BB stuff on Ebay, watch for fresh water items. Try to make an event there are usually a few props to be tried, there are quite a few members down in the Lone Star state with quite a few 22's

Phil

pmreed
06-05-2006, 09:20 PM
That motor will get you very close to 70mph if not actually there. You might look at props; what are you using now, a 23 Mirage + as a guess.
You can free up a few horses by changing the stock cast iron, exhaust manifolds to freer breathing manifolds such as Stainless Marine. You also lighten the stern by 100 pounds or so.
A lot of people swear by a K & N air filter to help breathing on the intake end. I don't know what that's actually worth, but I've got one that came with my 22.
The right prop and better exhaust manifolds will get you to 70, all else being equal. It's expensive, but a shorter lower unit, such as the Imco could give you as much as a 3 mph boost. After that, you're pretty much into motor mods.
As an aside, if you've got the standard Bennett trim tabs, check their fully up position. If the ends aren't a least an inch above the horizontal, they may be dragging = loss of speed. Not a lot, but the fix is free:smile: Look here (http://www.donzi.net/forums/showthread.php?t=33672&highlight=Bennett+tabs) for more info.

Phil

DudeHoss
06-05-2006, 11:36 PM
Thank you so much for the advice. That is a great idea. Your thread was perfect. Was I right on the horsepower of the 454 Magnum. After I adjust the trim tabs I'll get new exhaust manifolds. Are we talking headers or what? Will the aftermarket exhaust still allow the silent choice to work properly? Thanks again for your time and input. Lastly, are there donzi meets down here in Texas? I was thinking I'd has to come up north so I can hang with you guys...

DudeHoss
06-05-2006, 11:40 PM
http://www.donzi.net/forums/showthread.php?t=42068

Does the intake/flame arrestor that Dwight has help???

MOP
06-06-2006, 06:14 AM
Headers are the best way to go, why waste $$ on some half azz setup. You can find deals on used stuff at about 1/2 of new, but if you don't mind dropping some change go for Stainless Marine they are one of the better setups.

Woodsy
06-06-2006, 07:18 AM
Hoss...

Is your motor MPI/EFI? If its an MPI/EFI motor you will need to have the ECM reflashed/reprogrammed if you add the exhaust and hi-flow flame arrestor. The EFI motors have a tendency to lean out at WOT...

AZ Speed & Marine sells a kit for the EFI motors about $1k that includes a Hi Flow Flame Arrestor, MSD Ignition box and a computer reflash. You need to up your fuel pressure too...

Woodsy

DudeHoss
06-06-2006, 08:40 AM
Hey Woodsy

My 454 is straight up carbureted. Is it only the EFI engines that lean out too much or should that be a concern of mine with a factory carburetor? I’d like to upgrade the carb. But I don’t know what to go with and or what would be better than factory. Is an MSD ignition going to help my situation before I make a carburetor change or only after?

Woodsy
06-06-2006, 08:45 AM
No worries if your carbed...

I think the carb models were 365 HP and the EFI models were 385 HP... at the prop...

Woodsy

DudeHoss
06-06-2006, 10:22 AM
Sounds like I have some work to do to get the HP I'm looking for. I want to be in the 70's. There are some big boats on my lake and I need to destroy!

TMANN
06-06-2006, 06:09 PM
Where are you located in Texas?

TMANN

DudeHoss
06-07-2006, 01:22 AM
Hey TMann...

I live in Grapevine, TX out on Grapevine Lake. It's located in the middle of the DFW area. How many Donzi owners do you know in our area?

Pismo
06-07-2006, 08:36 PM
You have a Gen VI 454 with the roller cam setup and forged internals. 365 pshp carb, 385 pshp MPI. The KN arrestor will do nothing without an exhaust swap, not enough flow yet. Stainless marine is the way to go if you want to keep the switch exhaust, CMI if you don't. Stainless has a model that will work with your switchable exhaust, CMI does not. With the exhaust on then the KN may do some good. The MSD box will do nothing except breakdown more often than the stock merc ignition. Get the exhaust, then the KN filter, get a labbed 25" Mirage plus prop. You may need to rejet the carb but that is easy. Clean the bottom. You'll be in the 70s. Needs lots of trim for top end. Good luck. Easier to upgrade the carbed versions, heads and cam would be next.

Sofa King
06-07-2006, 09:05 PM
Hey there DudeHoss, They make good mattresses in Grapevine.

Arip

Sofa King
06-07-2006, 09:10 PM
I saw a price for Stainless Marine headers $1800!!!!!!!

zimm17
06-08-2006, 12:48 PM
I have the same engine. I went with Dana Marine exhaust. Very nice stuff, but they are bit wider than stock and my exhaust tips don't line up- off about 1" which makes it really hard to line up the bolts while getting the flexible hose to move over. I'd go with Stainless Marine.

I also changed the intake to an Edelbrock performer rpm airgap.

I picked up a couple mph, not worth the $2500 it took.

Get a portable GPS to measure speed.

I like my turbo 1 25p prop, but it'll blow out coming on plane if I use over 3000rpm. Someday I'd like to try a hydromotive.

Best speed so far is 71.4mph with full tank and two adults. That's at 4800rpm so if I go down to a 24p prop, I might squeek another mph or two.

I was ready to take the $20,000 plunge for a built 540 and the required full hyd. steering, but then I figure that costs more than the boat did in the first place. Is it really worth all that to hit 85mph? And the resale value doesn't go up.

I'm going to just enjoy it for now.

lakesnake
06-09-2006, 09:30 AM
I don't get it.....i am a new owner of a donzi classic too, and i have no desire to go over 70 mph...don't get me wrong, i love speed. However, it cost too much $$$ for such little gains...plus, the majority of the time you cannot even get close to 70 because of the rough and choppy water conditions (most texas lakes)...or you got a bigger set of balls then me...i enjoy having a classic boat and the attention that comes with it....enjoy the boat, beer, and bitches (sorry ladies) and when that big baja wants run with you just laugh and think to yourself, "i am in a donzi CLASSIC, i don't have to race anyone....it is all about class baby." enough said.

Pismo
06-09-2006, 02:19 PM
I don't get it.....i am a new owner of a donzi classic too, and i have no desire to go over 70 mph...don't get me wrong, i love speed. However, it cost too much $$$ for such little gains...plus, the majority of the time you cannot even get close to 70 because of the rough and choppy water conditions (most texas lakes)...or you got a bigger set of balls then me...i enjoy having a classic boat and the attention that comes with it....enjoy the boat, beer, and bitches (sorry ladies) and when that big baja wants run with you just laugh and think to yourself, "i am in a donzi CLASSIC, i don't have to race anyone....it is all about class baby." enough said.

I am beginning to agree with this train of thought. 75mph in my 22 is fast enough. Any further and I will have to install steering for $3-4k, then the upgrades for another $2-4k, new props, etc. So much $$ for so little. The thing I like the most about having a highly powered boat is the ability to cruise all day at 2500rpm at good speed and the ability to plane easily all the time. Top end is doing less for me all the time.

BigGrizzly
06-09-2006, 10:21 PM
I do agree with you guys about the speed. When I started my project my goal was to run 70 with the drive in neutral trim( ventilation plate level with the bottom of the boat). As the engine progressed and horse power was added my goal long passed. Yes I did the steering but refuse to use my money for a labbed prop for that igsignificant speed gain, besides so far stock props on my setup work great and better than any labbed ones I've tried. when you lab one you always give something up. Don't knock hydraulic steering there is more to it than HP. The steering does support the gimble housing and makes handleing more precise. Price a gimble lately. I am a boat, motorcycle and mussel car nut. I don't buy the latest CD or DVD out, my computers last more than 3 years, I don't chase women anymore. This may sound boring to you but when I am in my boat I have everything i need or want. REMBER this if your boat can go 80+ (and mine does) it doesn't mean you have to go fast, youcan just cruise. My problem is some of Donzi friends cruise faster than others. When your at Cumberland with Road trip, Doc Dan, Byron and others it is a blast, especially when they are good and safe drivers, Just to set the rechord straight I normaly cruise between 2800 and 3400 rpms about 40 to 54 mph.

blackhawk
06-12-2006, 03:45 PM
Everyone enjoys boating for different reasons. For me it is running trimmed out and WFO in some decent chop. Flat water bores me. The only time I ever cruise is when I am putting on some miles and need to cruise so I don't run out of gas. Otherwise I am chilling at idle or running WFO. And I love to race other boats. Win or lose I think it's a rush running with 3-4 other boats.

I agree it takes some serious $$$ to pick up some speed which is discouraging. My new boat(Pantera 24) runs a consistant 70 and I would love to pick up 8-10 mph but it would cost some serious $$$.

As far as labbing props it seems that there some good companies out there right now that are doing excellent work and people are seeing solid 2 mph gains. Like Zimm said, many spend $2-3000 for 2 mph!