need sugestion !

[RAKY0311]

I have a 23 Formula that i want to repower with a 500 hp and a jet drive,is that a crazy idea?,i dont know if i can use a jet drive with this hull because the hull have 24 deg deadrise,how can be the performance of the boat with this configurations?

all opinions are more than welcome,thanks in advance !

[redtech]

look at www.ultradynamics.com or hamilton jet form new zealand
ultra dynamics is from england telephone:+44(0) 1242 707900
sorry don't recall hamiltons phone #

[tja]

That is a lot of dead rise for a jet drive. I would think that a surface drive would work much better with that kind of horse power. Sincerely, Tom.

[RAKY0311]

thanks for help,i like the idea of the surface drive,do you know what especific unit i have to look for?

[tja]

Hello, I haven't looked at any resently but if you do a google search for marine surface drives you will find a lot of manufacturers. If i have time i'll see what i can find and let you know. From what i've read surface drives are more economical then I/O or inboards. With some research I think you will find several other advantages. Good luck. Sincerely, Tom.

[marshmat]

RAKY,
The way I see it, you're dealing with a fairly heavy, fairly sharp-V hull. The hull modifications needed to get a jet drive to fit and function efficiently would be pretty extreme.
Surface drives have their place, and properly spec'd can be quite efficient at higher speeds. I've never driven a surface-drive powerboat, but from what I've seen and heard it is very difficult to get them set up properly, and then you need to pay constant attention to the trim and instruments to keep an appropriate load on the engine for the chosen throttle setting. They're not exactly renowned for low-speed agility either. The upside is that you can get an awful lot of thrust with very little parasitic drag.
What was your old engine? A 7.4 with a Bravo I, by any chance? Or a V-drive? The Bravo's a popular and fairly sturdy drive; there are good reasons why it is the standard on so many performance boats (relatively cheap, durable, huge dealer network, adaptable to many engines, great choice of props, fairly efficient). Before jumping at a technology substantially different from what your boat currently has, it would be good to make a complete list of your criteria and requirements- you might be surprised where your needs actually end up leading you.

[RAKY0311]

thanks for help,very nice explanation,my hull is a 1973 hull but i take all out and redo with foam,so i'm sure that my weight is less now,yes i can use a bravo unit but a new unit with a transom plate cost more than 8000$ in USA thats why i consider the jet (3000$ new unit),i dont know how much cost a surface drive unit and i dont have experience driven one so i listenig to all sugestion.