hydraulic drive

[catalac08]

want to replace 30hp tohatsu 2 stroke outboard on a cat with a diesel engine similar size (nothing wrong with the Tohatsu, am very pleased with it but cost and consumption of petrol and availability at quaysides in Wales is a problem, also the big problem with outboards is the very limited charging capability which can be a problem on night passages running at a net battery drain.
looking for expereince of hydraulic drive as it would be convenient to site an engine in one of the cavernous lockers rather than fill up the cockpit. I would just hav a drive leg and (hopefully) small torque converter or similar hydraulic gearbox/drive with some hydraulic piping from the engine to the drive.
I know nothing about this subject so any comments on cost, potential problems, good equipment, bad equipment, common mistakes will all be very helpful in my doing the bst I can. /forums/images/graemlins/mad.gif

 

[WayneS]

I know that the later versions of the Heavenly Twins had this as an option. It may we worth while contacting Multihull World in Emsworth as they would have first hand experience.

W

 

[bdsweeting]

This could get you started on your search.....

http://www.peachment.co.uk/drive.asp

 

[boatbuilder]

Yes I have seen it done many ways on cats, and all have been a compromise in one way or the other. There is a big power loss from pump to drive and you need to keep the fluid cool , so that means a fairly big tank.
The good news is that you can put the engine anywhere you like. One boat here has the hydraulic motor bolted onto an outboard leg wich seems to work.

 

[Victorious]

I am Very very pleased with Hydraulic drive on Victorious.

all the major components were supplied by these guys
http://www.ars-anglian-diesels.co.uk/

 

[bendyone]

Golderarrow marine in Newhaven sell all the bits

http://www.goldenarrow.co.uk/

 

[Talbot]

Alternative approach is to go electric. Sillette sonic have electric drives that are suitable plus a single diesel generator?

 

[homa]

All I can add is the following from when I owned a Shipman 28 with hydraulic drive:

The engine can be monted anywhere and at any angle.
There is definitely power loss - but presumably if starting from scratch you can put in a bigger engine to compensate for this.
Very little maintenance on the drive system, I only ever changed the oil once.
Less wear and tear - can go from ahead to reverse at high revs - usefull if just run aground!
V.Quiet - as engine and shaft not rigidly connected - less rattle - engine can be mounted on soft(er) mounts.

I didn't have a cooling/header tank problem as mentioned elsewhere, but then I didn't have a very big engine (Farryman 12hp)

Apart from the power loss I can't think of another significant disadvantage.

 

[scottie]

Speak to sillette

 

[boatmike]

Advantages.
Can locate engine where you like.
No alignment problems.
Excellent manouverability, but no better than twin diesels.

Disadvantages.
No weight reduction ( heavier than two saildrive diesels usually)
Loss of efficiency requires bigger heavier engine
Higher fuel consumption means bigger tanks
Noisy pumps in addition to diesel noise
All your eggs in one basket. Twin diesels give back up if one fails.
More expensive than twin saildrive units.
Even more to maintain.

Personal opinion? Twin saildrive diesels with Autoprops on... superb!

 

[Boathook]

Fit a 15hp high thrust 4 stroke. Better fuel economy and possibly just as fast on the 8m. Not to sure whether the expense of converting to diesel inboard is woth it.