Arneson Surface Drives

[the3car]

Greetings all...I would like to discuss the concept of surface drives and why Arneson is the "defacto" standard in the industry.

The concept is not really that hard to grasp, pipe the power straight to the prop, keep the prop half-in/half-out, and be able to steer. I got a quote for a pair of ASD drives, $26K A PIECE!!! Why the expense? Is it because there is no volume, and thus the HUGE mark up?

Has anyone seen surface drives for say, $10K per drive? Seems like the casting should be cheap, the bearings cheap, and a u-joint, cheap as well?

Can anyone help?

From a performance aspect, looks like this is the wave of the future. Why hasn't Mercruiser picked up on the idea?

Any thoughts appreciated.

 

[MikeHalloran]

Arneson drives are big, made of corrosion resistant alloys, and in every one I've seen, beautifully finished. The finish is a requirement of the toy boat/ yacht market they're sold in; perfection is the standard for everything. The buyers in that market are careful with their money, but not price- sensitive in the usual way. For one thing, they know that good marine castings, bearings, and u-joints are not cheap.

Mercruiser sells to volume markets, comprising boats that are typically too small to tolerate the axial length of an Arneson drive. They do have a joint venture with Cummins, Cummins Mercruiser Diesel, that sells into markets shared with Arneson. Maybe they have something on the back burner; I wouldn't know.

Since Mercruiser has been sued for swimmer deaths associated with unshrouded propellers on ordinary outboards, I assume their legal and PR departments would have a heart attack over any production plans for exposed projecting cleavers.

There are, or at least were, other surface piercing drive manufacturers. I'm a little fuzzy on the details, but I have been told that the technology is not universally magical.




Mike Halloran
Pembroke Pines, FL, USA

 

[pauljohn]

Those must be small drives or in not very good condition. I looked after an eighty foot Italian boat that had Arnesons and the props alone cost $30,000.

Mike is right, they are well made and have very small tolerances in the drive units for them to work properly. They may look simple but they have fairly big rams to raise, lower and steer the units and are very sensitive to incorrect adjustments. Add all that expensive low corrosion materials on the hydraulics and the electronic control units and it is easy to understand where the money goes.

But when you drive a boat like that at 50 knots you can understand how it seduces the wealthy.

By the way the props are for sale, they are brand new, have never been fitted on the boat and will probably sell for half the original cost.

 

[raffshore]

http://www.dbdmarine.com

have a nice drive, same principle

 

[the3car]

Thanks guys for your postings.

There is another company...

http://www.q-spd.com

out of New Zealand that makes a similar setup.

What is really bothering me though, is that if the surface drives have lower drag, less moving parts, better efficiency, and comparable performance of a stern drive, then why aren't these drives going on boats of smaller, higher production volume, boats?

It seems to me, that the surfaces drives are a disruptive technology to the typical stern drives or outboard drives. Then I guess it's just a market demand problem. Until some higher volume boat companies switch over, they will remain very expensive and under used. Any comments would be appreciated.

 

[MikeHalloran]

I can think of a couple of reasons why you may not find them on production boats:

The props have to be trimmed half in/ half out of the water. On a 60 footer, you probably don't have to do it often; on an 18 footer, you'd have to re-trim for every added passenger.

Two, with steering mechanisms, just flat don't fit on the transom of a reasonably trailerable boat.

They're not easily shipped or installed in one piece. Handling the individual mounts, cylinders, hydraulic lines, etc., takes time and skill that's not in the budget of a production boat.

They _look_ dangerous. Common sterndrives are no less dangerous, but have fewer noticeable edges and pinch points, especially above the waterline.



Mike Halloran
Pembroke Pines, FL, USA

 

[the3car]

Thanks Mike.

You brought up some important points that I never thought of.

 

[pauljohn]

Also low speed manouevring is limited and backing up is terrible. The props just don't work well at low speeds or in reverse. Going up the New River in Lauderdale with the current behind is a nightmare.

With regards to trimming it doesn't matter what size boat it is, you have to constantly trim them. The units must be fully down to start and gradually moved to optimum as the boat gets up on a plane.

Another problem is marine growth. In warm water, eg. South Florida, the props have to be cleaned by a diver every two weeks or boat speed suffers badly. If you leave it for 5 or 6 weeks you won't even get up on a plane.