headhunter23

Well just as the topics states, how come? Yes I did not search, so if you want, bash away. Is it something to do with the mathematics? Too big etc?

Ivan.

McGary911

You see them a lot if you keep your eye out. They work very well.

Arneson surface drives are the most well known (www.arnesonmarine.com). Others such as BPM and Kaama (not made anymore) are out there as well. Mercury's speedmaster 6 drive is actually a surfacing drive, but doesn't look like the others. They typically need an external transmission, so most boats will have to have the engines moved up a bit to accomodate the tranny. Some claim that low speed handling isn't as good as a traditional drive. You see them in a lot of high performance applications, as well as big diesel installations. This is not only due to their efficiency, but their strength. No marine drive is unbreakable, but these are as close as you'll get.

Here are a few pics. First is a merc #6, second is a Kaama, third is an Arneson ASD-8 on a 120+ mph Donzi.....18' long. Wear depends.

Added another pic. Big Sunseeker with Arnesons. ASD-10s, it looks like.......

headhunter23

Interesting to see... still to be honest I have never seen one in person and I used to do a ton o boating around ontario.

You have any videos of them running? Are they more efficient than regular inboards or outboards?

Wheelnut

My Feedback: (81)

I would assume it cost alot of extra money and time in design, so there probably are half as many speed boats that have surface drives as do with subsurface drives.

ryan_t888

Firstly, our R/C boats are not fake if the full scalers are "real."

Surface drives are everywhere in racing for full scale!

Anythings from F1 tunnels to 125cc hydro's up to unlimited hydro's.

You don't find surface drives on the average leisure boat/fishing boat/recreational boat ect because of the disadvantages of surface drives.

Ryan

SV27dayton

Ofcourse the next question is what are the disadvantages? Ive seen the Merc alpha 1 used as a surface drive on a Stoker sport tunnel. and a Eliminatlor Daytona 21. Both were later converted to the blackhawk which were also surface but actually designed to be such. From my experience the disadvange was the airation on take-off. Similar to what I get with a small diameter prop. We used to ski behind it some times and you had to have the right prop or it couldn't pull you up. Which was kinda funny considering we were working with over 800HP! I like your pics, 911, they show that they aren't a new thing either.

doby

My Feedback: (1)

Hey Headhunter, I noticed you are from Waterloo, are you going to be out at Wellsley on the 29th for the RC boat races/display ??

ryan_t888

For surface Drive:

Advantages
- Avoids cavitation.
- Greater speed when compared to same boat with submerged drive.
- less drag

Disadvantages
- More difficult to turn
- Harder to set-up.
- Not efficient at low speeds
- poor acceleration due to aeration
- poor reversing

Ryan

hemiblas

Dont boats with surface drives shoot water 10' in the air (ok thats only the small ones). I would hate to see what a real one could do.

skidooguymxz550

because you've never seen a fast enough boat

SV27dayton

Yes the roost is similar. I wouldn't say that i've ever seen it go 50' in the air but with a little bit of trim you can knock a skier off the line (75' back) with a blip of the throttle. I've been on both ends of that exchange. At top speed (around 125 I guess its 25 up and 150 back.

headhunter23

Didn't know there was a show... what time?

Ivan.