Rik

I don't think you understand my comments. Not that getting 500 hp a side is hard, getting a 33' boat with twin 500 hp engines to 100 mph is hard..

That is an 1720 In Line Drive Unit, which are made for a diesel application not petrol. ( Late 1970's vintage) Your going to need some sort of internal drop/reduction unit in order to use these as the boat will not perform well with a 1:1 and to get that to hook up the engines would have to go really far forward. What you could do... Turn your engines 180 degrees in the boat. Install a "V Drive" at the back of a velvet drive transmission and this will give you the reduction and drop you will need. Rotation will have to be accomplished via a counter rotation engine or?

External rudder with the drives fixed is EXPENSIVE... Figure twin fixed trim cylinders, mounting area to be fabricated, then a rudder with steering... OUCH.. Plus your slow speed maneuvering is going to be very difficult with no vector'd thrust from the propellers.

Sleek Idea

The extension will be of new construction but, will effectively be like adding the back end of another boat. I've done a lot of searching to see how others have done this and this seems the best way. I won't get into the construction details in this thread. I'll start a build thread in a few weeks as I get some of the decisions finalized.

Sleek Idea

Ah, now I understand what you mean. Fortunately, adding horsepower is not too hard.

Been considering a couple of options. My first thought was to turn the engines around as you suggest only with a difference. I would run powerglides with a transfer case like a 4X4 would use. Inside the transfer case I can take care of gear ratio and rotational direction. From there a driveshaft to the surface drives.

The other option I was considering is a little crazier but, kinda cool. The engines could be installed inline with the transmissions offset and alongside the engine like you would have in a front wheel drive car. From there driveshafts to the surface drives.

Which solution gets used will depend on where the CG will need to be.




Yeah, I know. Glutton for punishment.

Sleek Idea

So, after all this. Does about 18-20 inches between the drives seem about right?

Rik

No less than the diameter of the propellers... So an 18" center would allow propellers no more than 18" with ZERO margin for growth so you will run a 17.5" or smaller... So, 19"-20" seems a smarter decision.

Rik

Powerglides.... Maybe they will handle the small block power.. They do build a bit of heat though. Velvet drive transmissions are shorter though which makes the engine room requirements easier.

In line engines with a 4X4 transfer case with the engine turned flywheel to flywheel handles the rotation change and the transfer case can handle the center distance. CG with this setup? The V drive offers the best CG situation.

Sleek Idea

Rik,

Thanks for the input. I'll be in touch when I get ready to rebuild the drives.

Cheers

BBADWS6

Looks like its going to be an intersting project. Subscribed.

hogie roll

Got a link? I've never seen anyone do this.

Sleek Idea

Here's how one guy did it. Not at all how I would do it but, it worked for him. He essentially sliced the boat in two across the stern and spliced in a section.
My thought is it's better to leave the transom as a bulkhead and create a new engine bay behind it.

http://forums.iboats.com/forum/boat-...ress-with-pics

Another example:
Sailing catamaran
http://www.time-for-a-catamaran-adve...then-hull.html