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Wood
07-23-2001, 04:25 PM
I have a 24 foot 1990 Donzi Black Window. It has an OMC Cobra outdrive with a 460 Cobra motor and a 12 pitch 3-blade prop.
I am looking for more speed from this boat. At 4500 RPMs I get 50mph max. I would like to put on a new CAM, a new carburator, a new intake, and new headers but keep the same motor.
Any advice you can give me would be greatly appreciated.

old rigger
07-23-2001, 08:19 PM
Wood,
In about 1988 or '89, during part of the time I was general manager of Advantage boats, we were approached by a couple of guys from OMC. They were trying to shake the bad stigma that the Cobra outdrives got when they were first introduced around '85. They were really crappy and had a ton of problems. The later ones were improved. Anyway these guys wanted to go racing and wanted to know if they supplied the outdrive and engine, would we build and campaign a boat? We chose the 21 Banshee, a little tunnel boat that I believe Harry Christensen (one of Advantages owners) splashed from a Eliminator. OMC wanted a record so we went after the ET II class record in the Kilo. The outdrive was set up with the propshaft even with the bottom of the hull and other than a nose cone and low water pick-up it was stock. The engine was a Mclaren prepped, single carbed, 454 (or 502, I can't remember). We set a new record at, 116 or 118 mph. Broke the old one by about 10 mph. I believe the record still stands today. We ran the Mississippi race twice with the boat and the Parker Enduro once, flipped it in the first turn.
I know that this is nothing close to the set up you have, but I thought you might want to know that these units a pretty tough. I have never owned one but maybe someone else can give you some insight as to how these hold up over the long haul. (the later units) I'd dump some HP in front of it and go for it.

spectras only
07-23-2001, 08:28 PM
I think the later units were 2 piece shafts or improved splines [don't remember]and were coupled to 460 King cobras .They can withstand up to 500 HP
[This message has been edited by spectras only (edited July 23, 2001).]

25 Outlaw 502
07-24-2001, 08:29 AM
I used to have a 1986 23' Stingray with a Cobra Drive. When I finally got rid of the boat it had a 406 Chevy with all the tricks. I would turn a 26 pitch 3 blade Raker prop at 5100 rpm and never had any problems with the drive. I was easy on it off the line and very carefull not to bring the drive out off the water at WOT as advised by several people. By the way if you get some more power and are looking for a prop I kept the 26 after trading in the boat and would love to get rid of it since I know have a Bravo Drive. I have it listed in Propswap.com or just send me an email if you are interested. I also had a nosecone installed with the standard pickup and it helped stability quite a bit at high speeds. The only real fear I had was I couldn't find anybody who made an external steering system for the drive and I have always been told to have it once you get 70+ mph. Good luck and I love the lines of the old Donzi's.
Larry

not guilty
08-01-2001, 10:33 PM
WOOD
Good to here from another of us off-breeds,i'm currently running a similar set up in a 86 mach-1.Built a new 460 (+.060)last year 475 hp.have had the boat since 1994 with a stock 460 (365 hp) until 97 ran a 425hp 429.guess what.NO OUTDRIVE TROUBLES AT ALL!!!!!!the original owner is a good friend of mine and he had no trouble since it was built(other than those nasty micro switches in the shift box,keep them working right or you'll have the lower apart real soon)I've talked to few shops that even know a cobra,but all say there good for 650 hp. by the way mine is the first gen. king cobra(pre-89)and i've been told these are the tough ones.As for hp in yours,be real carefull with the cam,if add much over stock with a ford reversion is serious,get some good after market exhaust(I chose EDDI MARINE THUNDERS,nice performance,nice price)as far as intakes,if you do much head work & other internals dont get any thing but ford svo or an offy.the stock cast fords are a good flowing intake.If you really want an alum. that will do good job without doing internals send me an e-mail, think i have a streetmaster & a tourqer-2.Biggest advice,get rid of the old cast exhaust ASAP,take it from exp.then play with the the motor goodies.And dont worry about the cobra, i'll pay FED-EX to send me the parts to believe it!!!!!!!
ps. your prop at 12 pitch had to be a misprint! 21???????????????????????

spectras only
08-02-2001, 08:09 AM
Wood,if I'm not mistaken,the OMC King Cobra leg was taken from their performance outboard ,the V-8 that had 8 carburator and 500 HP. I'm sure that O/B didn't have the same torque as a BBF,only the HP at high speed.So I would be careful not to go much over the 500 HP mark,or would be easy on take offs to save the leg internals.Bayliners put 460 King Cobras in their 28 foot command bridge models after 1989 when they found the 350's too weak.I talked to some owners and they were happy with the combo.