Building My Own Saildrive

[ya-jokin]

OK here goes, using an older (cheaper) bottom leg off an outboard - 300 HP, I bolt the unit to my hull through the cav plate to hull, using epoxy to bed it getting the right fit, removing it and reinstall with appropriate gunk to get a water seal.
Now the engineering bit, to have the vertical shaft attach to the flywheel of the diesel engine.... this would entail cutting and machining it to fit a right angle gear box, having the shaft now at the correct height as the center of the flywheel.

Who thinks this would work? And any ideas how?
A neat nutcracker!

Additionally, having the "saildrive" being able to turn - steering all sorted too - no rudder needed.

I'm building an Alaskan Trawler - 32 ft, I want 300 HP diesel and the means to get that HP to a prob cheaper than say a V drive or the usual stern leg.
This needs a higher reving diesel as the prop would be smaller to fit the "saildrive" or perhaps gearing in the right angle box changes the rpm of the prop. Perfer not to have to turbo or super charge a diesel with it's probable associated heating problems.

[delmarrey]

Originally Posted by ya-jokin

OK here goes, using an older (cheaper) bottom leg off an outboard - 300 HP, I bolt the unit to my hull through the cav plate to hull, using epoxy to bed it getting the right fit, removing it and reinstall with appropriate gunk to get a water seal.
Now the engineering bit, to have the vertical shaft attach to the flywheel of the diesel engine.... this would entail cutting and machining it to fit a right angle gear box, having the shaft now at the correct height as the center of the flywheel.

Who thinks this would work? And any ideas how?
A neat nutcracker!

Additionally, having the "saildrive" being able to turn - steering all sorted too - no rudder needed.

I'm building an Alaskan Trawler - 32 ft, I want 300 HP diesel and the means to get that HP to a prob cheaper than say a V drive or the usual stern leg.
This needs a higher reving diesel as the prop would be smaller to fit the "saildrive" or perhaps gearing in the right angle box changes the rpm of the prop. Perfer not to have to turbo or super charge a diesel with it's probable associated heating problems.

Anything is possible if you have the money, knowledge and machinery available. But why not install something you can get parts for easily?

[Lagoon4us]

Originally Posted by ya-jokin

OK here goes, using an older (cheaper) bottom leg off an outboard - 300 HP, I bolt the unit to my hull through the cav plate to hull, using epoxy to bed it getting the right fit, removing it and reinstall with appropriate gunk to get a water seal.
Now the engineering bit, to have the vertical shaft attach to the flywheel of the diesel engine.... this would entail cutting and machining it to fit a right angle gear box, having the shaft now at the correct height as the center of the flywheel.

Who thinks this would work? And any ideas how?
A neat nutcracker!

Additionally, having the "saildrive" being able to turn - steering all sorted too - no rudder needed.

I'm building an Alaskan Trawler - 32 ft, I want 300 HP diesel and the means to get that HP to a prob cheaper than say a V drive or the usual stern leg.
This needs a higher reving diesel as the prop would be smaller to fit the "saildrive" or perhaps gearing in the right angle box changes the rpm of the prop. Perfer not to have to turbo or super charge a diesel with it's probable associated heating problems.

Amongst a few problems with your idea the first is Torque..... Check out values from the outboard as against the diesel.
Second are you intending to fix the leg solidly to the hull?
How if bolted to the cav plate are you then able to steer it??? Sorry i may be missing something in your explanation. CHEERS..

[IslandHopper]

So if im reading this right, you want to build something like an "L-Drive Azimuth Thruster".....?

Azimuth Thrusters

[Lagoon4us]

Originally Posted by IslandHopper

So if im reading this right, you want to build something like an "L-Drive Azimuth Thruster".....?

Azimuth Thrusters

Hey there iv'e equipped a few boats with these, good gear also Schottells. i don't understand if you bolt through the hull via the cav plate how he would be able to use the steering mechanism from the original leg??? Or is he justjokin?

[sea-bee]

What about an electric motor on the top of an old outboard leg?

I know this won't provide the power required by the OP, but would that make a cheap electric drive?

[Lagoon4us]

Why not get on with enjoying the destination rather than wheel inventing?

[atoll]

ready made stearn drives,page 12 upto 450 hp

http://www.lancingmarine.com/databookV.pdf

[bobconnie]

Well something to think about ! 300 high rpm gas horsepower, and 300 diesel torque horsepower are two different things !! a 300 horse power diesel will tear that outboard part apart like lumpy gravey, just athought ! Bob and Connie

[GordMay]

Greetings and welcome aboard the CF, ya-jokin.

[IslandHopper]

Originally Posted by Lagoon4us

Or is he justjokin?

I would say so, there wouldn't be much left of the original leg after you have fabricated the 360° rotating assembly, you MAY be able to use the nut that holds the prop on.....

[JayCall]

The part that puzzles me is why do you want a 300 HP plant in a 32' trawler? I assume by trawler you mean a displacement hull. 300 HP would be about 150HP overpowered. I am 58', close to 50 tons, and I have two 158 HP John Deeres, hull speed about 11 knots. Even if you have a semi-planing hull, the diesel and the saildrive combo does not make much sense to me. The torque from a 300HP diesel running at speed to get you on plane will tear the sail drive apart, as was earlier noted. Might need to rethink your propulsion system.

[ya-jokin]

HAHAHAHAHAHAHAHAHAHAHAHAHAHAHA All plurry great replies for real! Thank you all, and yes it seems I was jokin..... no, was just an idea from a Kiwi boatbuilder - that needs a good long rest! On a boat..... that needs a motor.
Well after getting thoughts on just how much time and money I really need to spend as opposed to want, to get her in the tide, cheaper gets there sooner.
Just an aside, idea was, yup, was, to get the steering by way of some engineering work, wherein the cav plate wood've been attached to a water tight ring gear.

Again, cheers all of you for the replies.

Now, anyone have ideas on V drive with the prop in a tunnel, I read that some have had issues with cavitation, my worry is with the donk above the tunnel I loose buoyancy, and the tendency to squat when under power, I see so many over powered larger motor boats thundering along bum down - trying to climb their bow wave.

[atoll]

again lancing marine can supply,even if it is not in the catalogue,they can source stuff at very reasonable prices and ship anywhere in the world,they also custom build stuff.
give them a call 0044 1273 410025 they are all engineers and happy to chat.

i had a drive plate destroy it self in tanzania,phoned them up,3 days later i had a plate in my hands in dar-es-salaam!


http://www.lancingmarine.com/databookV.pdf

[James S]

A few years back I looked at a hombuilt 70ft cat on the hard, built by a local guy. He did a home build very much like what you are describing...As I recalled used small Isuzu's for the engines...his worked but he had a lot of noise from the 90deg gearboxes...He was worried about longevity.
His didn't rotate.