diy surface drive?

[boatguy64]

My friend was a guy named Scott Schoell. He was Harry's nephew. We built our own drive and was very sucsessful. Did you work it out or are you still looking? It is not as hard as it may seem.

[TerryKing]

Originally Posted by boatguy64

We built our own drive and was very successful. Did you work it out or are you still looking? It is not as hard as it may seem.

I'm very interested in building a DIY drive. I have some mechanical design / machining / welding background. Can you point to any info/photos of what you did??

Thanks!

[boatguy64]

I don't have photos. But I can build it. The design is in my head, you know. I might could explain it

[Frosty]

Thers nothing technical about a surface drive . It is simply mounting the propellor on the surface.

The problems come with just that--holding it there.

There lots of manufactures out there claiming theres is best.

Its the boat-engine- gearbox- and prop that does it.

Some steer by rudders and some steer by moving the whole drive. It would appear therefore that any configeration can work if applied correctly.

I myself have also made a surface drive system and mounted this system on a brand new boat, (at considerable financial risk).

Im happy to say that they were succesfull and I can exeed the speed of the boat manufactures speed with slightly less HP.

However reversing has been a difficult problem to solve.

From not being able to reverse at all. to a reasonable reversing performance that I feel now is acceptable.

If I did this again reversing would be the first consideration.

Some one said to me "what do you bother about going backwards for"

Have you ever tried going into a marina on a breezy day with less than good reversing power,-- not recomended.

[boatguy64]

The issue regarding reverse is a serious consideration. It is possible to overcome. It depends on the hull design. We built the hull with a suface drive in mind from the begining. I will post some pics when I can.

[tom kane]

If you have a trimmable drive that drops down to 20 degree shaft angle,which is what an average fixed inboard drive is there should be no more problems reversing with a surface drive, than a conventional inboard drive.

[Frosty]

Originally Posted by tom kane

If you have a trimmable drive that drops down to 20 degree shaft angle,which is what an average fixed inboard drive is there should be no more problems reversing with a surface drive, than a conventional inboard drive.

Building in 20 degrees down is quite a bit of extra hydraulics and im still not convinced it will cure the problem. It would need to be a long shaft of the Arneson flavour.

I am not in favour of external hydralics on larger sea going vessels that live in marinas and or only get hauled out anually. Variable trim systems for these boats is almost impossible to maintain.

As Boatguy said it really does need very carefull consideration of the transom shape. As the prop is so high and on some boats of shallow draft the tips of the blades can be on the surface at rest. If you have a flat 0 degree transom the water from the top of the disc and some of the water from the lower part of the disc can accumulate to the extent of having as much thrust bouncing off the transom as there is whats left of forward thrust. Hence the boat doesnt move --infact can still move forward as the thrust bounces off the transom into forward thrust.

I recently designed some "reversing plates" to act as a dummy transom, but also tried to multipy available thrust by shaping the plates in a way to gather and concentrate all possible thrust under or to the side of the vessel's transom.

These were succesfull, but as being made in stainless steel they encouraged quite a bit of electrolisis. I have just replaced them with a fibre glass version.

[Willallison]

As Frosty suggests, it's not the angle of the thrust that's the problem - outboards and sterndrives run at essentially zero angle, and the back quite ok - it's the transom reversing or at least neutralising the thrust. My understanding is that a transom angle of around 45 degrees can overcome it - at least to the point where reversing is acceptable

[boatguy64]

Harry Schoell's PSI drive or Pulse drive is an excelent solution to a lot of the problems discused here.

[mydauphin]

Hi guys,

I have my boat ready to go with custom home made Surface drives. My problem is I need something like thrust bearing on the aquadrive. I cant find anything reasonably priced. Aquadrive and Python Drive are very expensive. Found thrust bearings but no housing to put them in. I would have to machine something. Anyway, I see a lot of money going out the door. Anyone found a way around this. thanks

[tom kane]

Have a look at SKF "FY" Bearing housings.I have used these in trimmable S/Drives.They can be used as self aligning or variable shaft angles for trimmable drives.

[tom kane]

There are many ways to set up a fixed or trimmable S/P drive shaft.Image shows a 1960`s trimmable drive used for 30 years,with the choice of running in S/P or subsurface drive.Patent was granted 1973 NZ patent no 169862.The drive can be trimmed from the helm using cable,linkages,or hydraulics.Prop shaft is in a torque tube with water lube brgs at the prop and half way up at water level.The drive can run down to 20 degree shaft angle or lifted to adjust running depth.Because the prop is at an angle the decending blades have a greater pitch angle and hold the prop shaft down while running.The water gland does not leak because it would usually be above water level unlike glands fitted at the keelson.While running shaft torsion effect lubes and cools the water gland.Motor is usually at 10 degrees angle and twin u/v`s with sliding spline give 10 degrees up and down movement using SKF "YF" series housing and thrust brg.Motor,thrust brg,all of the drive is soft rubber mounted and runs super smooth.

[mydauphin]

The boat lwl 60 feet, 15 foot beam, 3 foot draft, weight 40klb Aluminum Planing hull, Twin DD 671 450 hp, 2-3/4 shafts, tranny 2 to1, lots of torque.

Those SKF bearings are too small, I am looking at a back to back set of 29413 E in a custom housing so far.

The whole setup is similar to power-vent with rudders inboard of props. The drive would be fixed at about 5 degrees. Shafts within tubes. Props would be about 5 feet out of transom. Transom is at 45 degrees and was originally setup for Arnesons. They are similar in size to a ASD10


The rudders are fixed with the rudders separating the prop wash so that reverse and slow speed will handle similar to non-surface drives. I have even considered one big rudder, but I would get zero prop effect on rudder and would make handling more difficult.

I have most of the parts except bearings ready to go - I am not happy having to custom make bearing housing so I am still looking for a better solution.

Many have suggested straight shaft but I am sure of after the fact adjustment to shaft angle to achieve maximum results

I am looking for simplicity, lowest cost, and performance.

I'll post some drawing when I finish them.

[tom kane]

The bearings suggested are available in 2 inch shaft and bigger and are used in big hydroplanes doing 180+ MPH.The same set up is used in heavy earth moving and leveling equipment.

[mydauphin]

Originally Posted by tom kane

The bearings suggested are available in 2 inch shaft and bigger and are used in big hydroplanes doing 180+ MPH.The same set up is used in heavy earth moving and leveling equipment.

I am having trouble finding it on 2 3/4 shaft size. Do you know a part# ?
Much Thanks

tony