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CDMA
09-12-2002, 09:40 PM
The advantages of Stainless marine on an 18…

I have done a lot of things to my 18 over the last 3 years and without question the single best was my switch to stainless marine manifolds. I figured I would fill you all in. Over the last winter I put a 383 SBC in my 18. This engine was built on a budget and at the time I built it I was not sure if I would be able to afford anything other then the stock exhaust I already had. For these reasons I built a very mild 383 with a small flat tappet cam that would not have reversion issues with stock manifolds. However during the process I was able to scrape together enough money to get the basic stainless marine aftermarket system.

The engine was completed this spring and was dynoed with the stainless marine exhausts. The engine made between 407 and 427 hp at 5200 rpm depending on the set up ( carb and timing).

After installing the engine in the boat I got into a rather heated discussion with a member whether the exhaust was really necessary. So being pigheaded and stubborn I decided I was going to find out for myself and put to rest in my mind whether it was worth it or not.

So I ran the boat with the Stainless marine exhaust and the boat ran 72.1 on gps with a 25 mirage.

The same day I swapped exhausts and less then two hours later the absolute best I could coax out of the boat was 68.3. With no other modifications I lost almost 300 rpm. It was enough I think had I kept the stock exhaust I would have been better off with a 23 mirage.

I have to say I was surprised at the difference and I never thought it would be that much. But for my application it was. The next time I went out with the stainless marine reinstalled the lost punch was gone and I was running back over 70.

The other advantage lies in weight…or lack there of. It isn’t very scientific but I really think the boat rides better w/o the 100 extra pounds in the rear. Installation is also easier. Instead of needing to muscle the manifold and riser into and out of the boat I can easily handle them. They are so light and easy to remove sometimes I find myself removing them just to make it easier to work on the engine.

So this is the end of my tirade. I just wanted to share with you my resounding success. I can not say how your results will vary but I can say for me it is the single best thing I have done to my boat. If anyone has any questions or wants to talk to me feel free to e mail me.

Since these tests I have further dialed in the boat and added another couple of miles per hour and now I am on to making the boat capable of dealing with the extra speed. It looks like imco external steering and bennet sport tabs are on my horizon.

Chris

Well exhausted... and I was right...they are worth it :D :D :D

Gritz
09-12-2002, 10:07 PM
Chris,
What brand?
What cost?

Cuda
09-13-2002, 12:08 AM
Things that make you go hmmmmmmmm! I have a mildly built 355/330 horse, stock merc exhuast and I am going to install switchable thru hulls, this might be a good time to do the whole thing. Do you think it would make as much difference on a more mildly built engine?

BigGrizzly
09-13-2002, 12:21 AM
Chris, two or more years ago I got into that sane discussion on this board, and told that I didn't know what I was talking about. "There are no restrictions in the stock exhaust" he said. I have done many back to back test, just to prove things arn't fluks. The fact is the more HP you have and the bigger the engine, the more gain you will get. I have to hand it to you I probably wouldn't have swapped them back. I started with stock and went up, never to go back again.

Randy owner of Donzi since 1966.

Gritz
09-13-2002, 12:27 AM
So Chris, you want to share the brand and cost or just gloat? LOL :rolleyes: :rolleyes: :rolleyes:

nasty habit
09-13-2002, 05:26 AM
Stainless Marine exhaust manifolds & long thru transom risers = approx $ 2095.00 plus shipping and tax add another $140 for the beauty ring and external flaps

CDMA
09-13-2002, 07:02 AM
What Scott said. My system was a little cheaper. I think "street price" is about $1400 for what I have.

http://www.donzi.net/photos/callard1983.jpg

Rootsy
09-13-2002, 08:04 AM
gotta love engineers...

truly does it have to do purely with backpressure or is it the ability of the stainless marine to scavenge cylinders which builds the extra power?

just one more thing to add to my "wish list" wink

thanks for the info Chris!

RickR
09-13-2002, 08:07 AM
I'll bet she sounds better with the Stainless Marine exhaust :D
I'm happy with my Trimmaster 12x12 Sport Tabs from CPPerformance. Trimmaster solved the leaking resevoir problem and I like the switch better than Bennetts.

waleyetwo
09-13-2002, 08:43 AM
SOUNDS GOOD THANKS CRIS FOR PASSING THAT INFO.
I'M THINKING OF PUTING SOMTHING ON MINE.NOT SURE WHAT I WOULD GAIN ON A STOCK 350 MPI BUT IT WOULD SOUND BETTER THAN GOING THREW THE TRANSOM.AND 4 INCH CANONS DO LOOK NICE.AND I WOULD LIKE IT TO SOUND LIKE A DONZI. :)

Forrest
09-13-2002, 08:58 AM
Everyone knows how much better your 16 or 18 Donzi runs when you get that big boy out of the back seat and back up on the dock. Well, it's the same effect when you toss 220 lb of cast iron out of the engine compartment and replace it with 60 lb of aluminum and stainless. Yea, the runners are super short in a Stainless Marine small-block manifold, but still, it's a much better design than stock, but they are no where close to being tube headers.

The order of improvement using Stainless Marine Exhaust over stock iron as I see it:

1. Weigh much less
2. Don't clog with rust
3. Looks great
4. Flow better

ToonaFish
09-13-2002, 09:22 AM
5. Adding a bright shiny object to your boat has a coolness factor of ten...

Gritz
09-13-2002, 09:39 AM
Chris,
Always impressed by a functional piece of art!
Sorry I missed the capital "S" in Stainless last night. Might have been the Shardonnay. :D

Digger
09-13-2002, 09:43 AM
OK I have to ask, even though it is a hypothetical question, there will be no one right answer,...etc etc.

this discussion has me really intrigued. your opinions please: what do you think I would gain by doing this to my boat? Assuming no other mod's are made (bone stock 502's, including manifolds, exhaust, and silent choice)
the motors will be out of the boat this winter, it would be the right time to upgrade.

RickR
09-13-2002, 10:43 AM
Digger
Mabe 1 or 2 mph. If your exhaust is 1996 vintage it may need to be replaced anyway. Hope that helps justify the cost wink

Digger
09-13-2002, 11:09 AM
thx Rick, mainfolds were replaced when I bought the boat... but I'll still be giving it some thought...

CDMA
09-13-2002, 11:14 AM
Digger. They make an even more economical version with an aluminum riser. I think I have seen them advertised for $999 a set. I don't think that is a heck of a lot more then OEM.

You might want to look into this.

Chris

EricG
09-13-2002, 01:18 PM
Great Post Chris....and very impressive results!

I'm curious if anyone has done this type of comparison on a Stock SBC? Every comparison I've seen has involved either a Stroker, or a bunch of other modifications when the exhaust was done. As Griz said, the more powerful the motor, the bigger the gain. I've also heard that most stock SBC's won't benefit a ton from just the exhaust, other than the weight decrease. I'm just curious if anyone has tested it?

I definitely think the upgrade is worth it just for the weight, sound, and look.....I really need my Stock manifolds to hurry up and Rust wink

EG

boxy
09-13-2002, 02:19 PM
Chris since you have finally posted pics and specs of your :rolleyes: "stock" :rolleyes: 350, are we to assume your Dad now knows what lives under the hatch .... :D

clayman
09-13-2002, 03:47 PM
I have been very happy with my SM exhaust, $1395 for manifolds with stainless risers, and $128 pair of 4" angle cut tips with internal flappers.
mine came with mounting brackets on both risers, but I didn't need the one side since I got rid of the stock ingition. So I ground it off and polished it up (red arrow), They look and sound great! http://www.donzi.net/photos/jspiroff75.jpg
James :)

CDMA
09-13-2002, 04:19 PM
Boxy,

Nah we are just going with the hope dad doesn't look at the site approach...

Baxter,

Port dipstick? If so what do you use? Having a bad time getting anything to fit well enough with the stainless marine.

Chris

CDMA
09-13-2002, 06:18 PM
Pale it was more like ghostly...

I have something set up like that but what I can't do is get it to clamp in place well enough so that a drop or two of oil doesn't seep out every time I run. How did you clamp your pipe in place? Any way you could possibly please please send me a picture?

Chris

Remembering we need a hood scoop w/o holes...check...Christian where are you???

EricG
09-13-2002, 06:35 PM
Thanks Poodle.....funny how much more you learn reading a little more slowly.... :rolleyes:

EG

pmreed
09-13-2002, 07:50 PM
Scott,
You know I've been planning on the Stainless Marine set-up for my 502. Count me in.

Phil

fasttrucker
09-13-2002, 09:05 PM
w.o.w., eek! someone else on this site loves my stainless marine manfolds,as much as me.my boat is 6mph faster with the system.5-yr warranty is nice too.i also added k+n flame erester,reprogramed ecu.wires, cap ,plugs.tune-up.ive got pictures hope to post soon :D p.s. i had the baffles taken out,larger flaps on the transom.

Long Island Boater
09-13-2002, 11:39 PM
CDMA,
When you did the swap to Stainless Marine, did all the accessory brackets(remote oil filter, etc.) come with the manifolds? Im just concerned with trying to locate new homes for these items if they cant return to thier original spot.
Thanks, Rob

CDMA
09-13-2002, 11:46 PM
Yes and No. The Stainless marine manifolds can be had with the accessory brackets. I chose to go without them because I don't like the look of all that stuff on the engine.

But yes they can be had to just swap in for what you have.

Chris

Me fits much better in 22 engine compartment...this is going to be fun :D :D :D