top speed of a 18' classic

[Moody Blu']

I know someone who is building a blueprinted chevy 350 engine for a 18' classic and throwing a bravo drive on the back.

I may be able to get his alpha drive for trading him for two stand up jetskis. :)

what is the top speed of that hull with an I/O???
the guys at some marina in shipbottom N.J. are telling the owner it will do 85mph +
isnt that more than that hull is capable of with an I/O????
it sounds a little to high to me what have you guys seen these hulls do?

Im sorry I posted a topic about18'classic hull speeds but im to lazy to look back for another topic about this.

[Scott Pearson]

Geoo is doing over 90mph with his X-18.

(NJ)Scott

[Moody Blu']

Scott!!! we missed you on saturday!!! :(
what drive is geo running an arneson?
or a I/O?
Im trying to figure out realistically what this guys boat is gonna do.

[GEOO]

Broque, When I had a Volvo "E" Drive
(speedmaster) with the best conditions she would run 80mph with some chine walking. I had a 383ci chevy approx 360-400hp.
The Volvo speedmaster drive is 2-3 mph faster then a Bravo.
I think a Bravo equiped 18 could run in the 90's with the hp and proper set up.
My guess would be 300hp 68-70 (crank hp)
400hp 74-77
500hp 80-85
600hp 88-92
A built chevy 350 will probally make 350-400 hp at the crank. My guess would be he will run 70-74mph . GEOO

[Moody Blu']

geoo can you still purchase volvo speedmaster drives??
anything that is better than a bravo sounds great to me.
my 250 drive is in good shape but needs a complete freshening up, so forget that!
I'd rather spend the money towards a new drive.

[GEOO]

NO, stopped making them in the late 70's or early 80's, parts and servicing is difficult. GEOO

[Moody Blu']

ahhhh fooey :o

[Moody Blu']

So what would be my best bet when I decide to switch to another BETTER drive.
alpha?
bravo?
volvo 270,290,sx,??
what will fit in the place of a volvo 250 drive?
gimbal and all??

[Forrest]

The only thing that will directly fit in the hole that your 250 came out of is a Volvo-Penta 270, 280, or 290 - all of which are no longer built. The 280T and 290 both have power trim which would be a real plus. Another drive that will fit in that hole with some modification is the Volvo-Penta DPx and DPxHP, but try to find one of these at a reasonable price. That leaves the Alpha One, Bravo One and Volvo SX as choices.

You could probably get by with an Alpha One since an 18 Donzi is not going load the drive as much as a larger boat does. The drawbacks to the Alpha One is mainly its outboard-motor type clutch-dog shifting mechanism and that it's pretty much a light-duty outdrive. The advantages of the Alpha on over the other drives is primarily price. Also, the Alpha One is lighter in weight and has less drag than most other outdrives due to it narrow profile. In your specific case, another advantage of the Alpha One is that you can easily mate a small block Ford the this drive. All you need is an early '70s Mercrusier 888 bellhousing and coupler.

Next up is the Bravo One, for this discussion includes any of its upgrade versions (i.e. HP, XR, etc.). This drive is pretty much the mainstay of the performance boating community. It features durable Volvo-Penta type cone clutches, and has undergone many improvements through the years to improve its reliability. The big drawback is price and that there is not all that many available on the used market. New Bravo One transom assemblies with trim rams are usually available on eBay for around $2500, and that does not include the drive! Another $2500 to $3000 will get you a used or rebuilt Bravo drive. Another drawback in your case will be finding parts to mate a Ford engine to the Bravo One drive.

Now comes the Volvo-Penta SX. This is a highly refined drive system. It started life as the OMC Cobra series back in the '80s. Great hydrodynamics and so-so internal hardware - that is until OMC's outdrive division was sold to Volvo-Penta. Volvo engineers refitted the entire outdrive with new gears, cone clutches, and better shafts. In terms of HP ratings, the Volvo SX is probably as durable as a Bravo One, and a lot more durable than an Alpha One. You may have a hard time finding a used Volvo SX drive though, but I hear that they are out there. Also the Volvo SX can use Mercury props that have the FlowTorq II hub, like the Mirage Plus, as well as the proven OMC Raker prop.

Forget the SSMs, TRS, and SternPowr. All of these require a hydraulic transmission between the engine and drive.

Tough choices, huh? :eek:


BTW. I have an X-18 with a mild 383 stroker Chevrolet (380 to 400 HP) coupled to TRS outdrive. It's not dialed in yet, but the best that I've seen with it is the mid to high sixtys. I'm probably loosing 50 or more HP through the hydraulic transmission, drive, and power steering, not to mention the extra weight of the TRS unit. Still, it's a fun Donzi to run. :D

[Moody Blu']

wow thanks forrest!!!
I want that sx!!!!when I have the cash Ill ask more questions.
damn decisions!!!