Shafts thru the transom?

From this I assume that you also installed new engines? If so, what kind were they...heavier / lighetr, more / less powerful, more / less efficient in themselves...?

 

Did you build this boat? You had the right idea just the wrong engineering.
As for the original question, Yes this is possible, and it does work, but your engineering has to be right on. There is alot variables you must consider in your design.

John

 

Q-spd

We have good results with this drive at sub 40 knots

 

Gonzo I don't understand why you say Surface drives are ineffeciant under 40 knots. Have you owned any? My boat is equipped with fixed surface drives. I cruise at 35mph 90% of the time. Thats where it runs the happiest. I get about .75 nmpg at that speed according to my floscan that is interfaced with a GPS. WOT I can get 50mph if lightly loaded. Thats not bad for a 16,000 lb boat with gas engines. I can cruise as slow as 25 mph with the tabs dropped and still show about .66 nmpg.

Now having said all that, I am removing the fixed drives and installing Arnesons. Two reasons, most importantly I got a deal on a set of used Arneson drives. Secondly the fixed drives are set at 10 degrees. Great for cruising but not so good for dock handling or high speed. It wants to lift the stern over 40mph causing the boat to bow steer. I have talked to other people with fixed drives, it seems most are set about 4 to 6 degrees.

Also there are many companys that make props these days because this set up is getting more popular all the time. I was quoted about 2,000 dollars from Osborne Propellers for a new set of 4 bladers. That was a few months ago before the dollar dropped. They are in Canada.

Not a very good pic of drives , but I think you will get the idea.

Steve H

 

At lower speeds an outdrive would be more practical. For example, it has better maneuverability. Also, high speed propellers are not efficient at lower speeds and viceversa. 25MPH is the high cruising range for most people. Maybe 35MPH is your best speed, but as a design type, surface piercing propellers and surface drives excell at higher speeds.

 

Surface drives will always do what surface drives do,try to lift the back of the boat until the prop rides on the prop hub,it can not go much further.These drives push hydroplanes at high speeds and the hull design can cope with that.A boat should be designed with the propulsion system as part of that design.Building just hulls an adding propulsion at the whim of the customer does not make a good performing boat.I have been running a drive for many years, that can run at any depth,if started at 20 degrees shaft angle power is applied,the drive stays at 20 degrees untill very high speed is reached.the drive has been used un-locked and is weight-less behind the boatat speed,over 40 years many props and different steering have been tried,including transom mounted jets and a jackable inboard/outboard drive.

 

Well to get back to Buck's original question.

Yes it has been tried before and it works very well!
you can use struts and conventioal rudders as long as they are mounted correctly. Mine has over 1,000 hours so far and it works.

Steve H

 

Steve.
When you replace the drives with arnesons what will you do with the hardwear you have? What size prop do you have and whould you want to sell any of it?

 

The shafts and related hardware will be available for sale. I have three sets of props. I will probably sell one set after I have done some testing with the Arnesons.

Prop sizes: 18X21, 18X19, 19X20

These types of props do come up on E-Bay occasionally.

 

shafts through the transom

A more user friendly inboard/outboard is one that can be run in surface piercing or subsurface mode by lifting the drive strait up and down(jacking) for more efficient and easy shallow water operation,and can kick back up and tilt,this helps with load tuning.Not having a drive that protrudes way back behind the boat on a trailer is great.

 

Steve,
What size shaft do you have, and is it keyed or splined?

 

It has 1 1/2" splined shafts. 19 splines, same as Arneson ASD6, 1720, 1721, Kaama, and some Mercs. Shafts are at least 60" long. so they would be adaptable to many different apps. I would want to sell as a package. Rudders, steering ram, helm, struts, shaft logs, etc. I am hauling boat out of the water in a couple of days. I will get some good pics if you are interested in seeing them.

Steve H

 

Any thing other than a normal straight in board/V-drive will not be cheap,
Props, shafts and fuel to feed these setups wont be cheap, so if this is a way to stay in a buget, be ready for more than you bargan for. This setup would basically be a surface drive and S-Drives are not economical there quick. If they were economical they would be on more boats. It also takes more power to get the advantages out of S-Drives,lots more power.Take a small off shore style boat with 500-700hp you can burn 200-300$ in fuel in a weekend easly.

 

I can only speak from personal experiance. Unless you have owned cared for and fed one yourself, you are just blowing smoke. I have owned and operated several different types of drive systems. Including conventional shaft drives, I/O, and jets. I much prefer the surface drive for larger offshore boats.

Steve H

 

An average marine workshop could easily build an inboard/Vdrive that could be run as a conventional drive,or as a drive that can be raised and lowered from horizontal or down 20 degrees shaft angle,or much more using mass produced components.You could have a choice of surface piercing or subsurface drive,and a choice of steering devices.Take a look at James R. Wynne 1960 inboard outboard patent and see how that works.There are many other systems used in modern applications.The cost should be minimal, even as one off units.