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j90
10-06-2005, 10:47 PM
I'm in the process of building a motor for a X 18. I am considering a 383 stroker apx 450hp. I am thinking of moving the drive up 2 inches and using a bravo with an Imco shortie. Does any one have any idea of apx. speeds this set up will run. Any information would be helpful. Also any other power choices any one would use.
Thanks,:wrench:

Lenny
10-06-2005, 11:03 PM
I'm in the process of building a motor for a X 18. I am considering a 383 stroker apx 450hp. I am thinking of moving the drive up 2 inches and using a bravo with an Imco shortie. Does any one have any idea of apx. speeds this set up will run. Any information would be helpful. Also any other power choices any one would use.
Thanks,:wrench:

Ted knows these numbers... I "assume" the two inches you are referring to is the IMCO, as applied to a "STOCK" hull. Ted has run "up" 3" on an 18. He will know the numbers. Raising the "X" and keeping a fat blob of metal in the water would probably NOT be as good as raising the "X" by doing it with a shorter lower (IMCO) and keep the low center of gravity of stock engine placement and its' hydrodynamic slipform...The IMCO is the way to go. Stock motor placement.

This confused me...
I am thinking of moving the drive up 2 inches and using a bravo with an Imco shortie.

The "X" and the Classic 18 are the same hull. No worries.

We want your YEAR and HULL # ... please ;) Very few "X's" we have numbers for... :D

Pics are an obvious MUST :eek:

Barry Phillips
10-07-2005, 12:05 AM
Geoo was running around 70 mph with his 425 hp 383 powered X18 and the original Volvo drive, not sure of the model, that came with the boat. He can give you the exact numbers though. I had a Classic 18 running a standard 250 hp 350 (5.7L), a Bravo 1 spinning 23" Vengeance wheel that obtained a confirmed 65 MPH with a passenger. If you set yours up right, mid 70s should be obtainable.

Lenny
10-07-2005, 12:18 AM
Geoo grabbed about 7-8 GPS mph by putting on an "E" lower and 1:34's. He had the ponies.

Slippery is the target...He ended up at about 82-84 I believe before the Arneson. The Arneson started out similar but with a ton of mods, another 400 horsepower, he now sees mid 120' s... :eek:

Dregsz
10-07-2005, 03:20 AM
I saw 64 mph on speedo w a 325 hp 350 chev and 22P Michican Wheel Raptor prop.
A 383 is an easy way to go, if price is not a consideration I would look at a big cube SBC Dart motor in the 415-434 CI range with a hydraulic roller cam. It's torque not HP that moves boats that's why the torquier 383 is a step up from the 350.
I would expect you could be in the mid 70s with the 383 and drive choice.
prop testing will be fun.

good luck

Barry Phillips
10-07-2005, 11:25 AM
I rode in Geoo's X18 before he changed to the A-Drive and he was not running 86 miles per hour, that I do know. He was running in the high 60s low 70s though. Even with a 425hp stroker no 18 is going to run 86 mph with a stock IO not to mention a Volvo from mid 70s. I rode in Geoo's boat again 3 years ago after he added the A-Drive and we saw 86 miles per hour on the speedo before the water conditions just made things to hairy to run faster. Only Geoo can add to this discussion since he built Mighty Mouse in the 1st place.

Lenny
10-07-2005, 01:05 PM
Barry, I remember a post a while back, and others 4-5 years ago where as he saw a large jump in speed from sticking on the "E" lower. I can't find the numbers but maybe I am wrong (most probably)

I remember his posts every few months with incremental speed increases. This was back in 2000-ish. I cant get the "Search" to go that far back as it max's out the 20 pages with the criteria I am putting in.


GEOO
Registered User Join Date: Mar 2000
Location: Fairfield, CT
Posts: 1,576

Scott, you have a good memory or data base?

Hum....But the rope and the fishing thing....

The E:drive requires an external water pick-up.
You need Hydralic External Steering!!!
My 383 made about 360-380hp ran 66-68 one day and 78 the next, just by bolting on the Erive Foot. She would go right up to 70 then play with the trim and you would find a sweet spot in the hull and it was like you hit the throttle again and she would accelerate up to 76-78.
__________________
FYI...Too go faster ......Wind Her Tighter....



Oops, you were right, high 70's :D with the "E" drive, not 80's

j90
10-07-2005, 01:15 PM
Thanks for all the help. To clarify; I was thinking of raising the motor 2 inches higher, hence raising the center of gravity and putting the imco shortie on. This would raise the drive apx. 4 inches over stock. Is this a good idea or not. I would like the boat to run 75-85 mph if I can do it without crazy power. I still want it reliable. Thanks.

Lenny
10-07-2005, 01:23 PM
:eek: , I wouldn't want to run at 4" raised "X".

Why not leave the C of G low (Stock) and go for a 2" shortie. You can go from 1-3" using their lowers. I am sure that will be more than enough, and you can buy 400 ft pound 383's from GM for $3800 bucks. That would definately put you exactly or further than your goal.

http://www.gmgoodwrench.com/perfparts/images/parts/large/12497317_large.jpg

http://www.imcomarine.com/pages/sterndrives.html

Rootsy
10-07-2005, 02:06 PM
i for a fact know of an 18 that handles unlike any other 18 i've ever been in @ +3 inches.. without worry of cavitation or blow-out or porpoise or ill handling... this is with an alpha SS which is at 3 inches shorter than a regular alpha / bravo so motor placement is as delivered from donzi... at around 400 ponies she will run on the verge of 80ish... but high 70's is more the norm...

i would not run the motor up any higher than i had to... maybe an inch max.. and then add the shortie to get you 3 inches... CG is a finicky kitty to be playing with...

J

Barry Phillips
10-07-2005, 03:30 PM
Geoo did get a big jump in top speed but it took the 383 stroker plus the A-drive and a lot of dialing in to get there.

As for J90’s goal, I would go for a 2" shorty not the 4” and 383 crate motor or find a good builder, 450 HP will get you were you want to be. There is a 377 Scorpion 18 on this sight that as I recall will run in the mid to high 70s. The 377 Scorpion made 355HP at the prop, and used a Bravo X or XR drive, I’m not sure. If you can find out the specs. and top end of a stock Scorpion 18, there is your baseline. Donzi only sold a handful these 18s because they were really pricey, as much or more expensive than a 496 HO equipped 22.

GEOO
10-07-2005, 09:53 PM
:wrench: My 383ci (approx. 400hp not dyno'd, AFR heads, Fuel injected, Stainless Marine Exhaust, Hyld roller cam) ran 67 mph with 290 Volvo, when I added the E:drive lower unit, ran high 70's almost touching 80. Think the E:drive is faster then a Bravo and a Bravo shortie. The E:drive is much smaller Dia. then a Bravo and is shorter then a standard Volvo.
Bravo/Shortie would be hard to get over 80 with a 383 or a 406ci small Block.
A 383ci will give you 6-7 mph? and a shortie ? 2-3mph?