Volvo twin prop Hydraulic powered by yanmar on Cat

[kjon38]

I found a well kept 30ft Endeavour Catamaran for my wife and I to cruise up an down the Florida East cast. The concern I have is the engine is a Yanmar pwering 2 Hydraulic Volvo's. I have never heard of this and dont know much about this set up (good/bad/indiufferent). Was wondering if someone here has heard or experienced this type of propulsion set up and what type of issues I could be facing. Seems to me it could be multi points of failure and more maintenance, but it could be a great find. Looking to get any feedback I can.

Thanks

Ken

[skipperpete]

Originally Posted by kjon38

I found a well kept 30ft Endeavour Catamaran for my wife and I to cruise up an down the Florida East cast. The concern I have is the engine is a Yanmar pwering 2 Hydraulic Volvo's. I have never heard of this and dont know much about this set up (good/bad/indiufferent). Was wondering if someone here has heard or experienced this type of propulsion set up and what type of issues I could be facing. Seems to me it could be multi points of failure and more maintenance, but it could be a great find. Looking to get any feedback I can.



Thanks



Ken

Hi Ken
Theoretically, the hydraulic drive system sounds like a good solution to getting the power to the propellers but the reality is that the efficiency loss and the added complexity defeat the purpose. I’ve seen and worked on several hydraulic drive installations that varied from the remarkably complex....... using variable displacement constant speed pumps and electro hydraulic directional control valves like on modern excavators down to very simple pump/motor hookups with manual directional control valves. All systems required a higher level of maintenance and understanding than a simple gearbox installation and you probably need to carry at least 20 litres of hydraulic oil in case of a loss of the system oil through a leaking seal or burst hose.
You also have the added complexity of a saildrive (which is actually a nifty idea and eliminates the need for reversing the hydraulic motors).
The windlass and other stuff can also be hydraulically driven ( emergency bilge pump; water maker pump, fridge compressor and on a Classic Sparkman and Stephens I saw a high amp Balmar alternator driven hydraulically).
These are my observations from personal experience and I hope they help you to reach a decision.
Pete.

[kjon38]

Thanks Skipperpete
Sounds like my original assessment was correct as to adding points of failure. It would be the perfect boat for us and the right size for us to sail, but being an older cat and with this hydraulic propulsion I don't think it is worth the risk.

Ken

[DougR]

Not so sure I read this the same way as SkipperPete.....

The title says “twin prop”....... this is terminology normally reserved for twin prop stern drives, such as the Volvo Penta Duo-Prop, or the Merc Bravo3. Is that what you have? Or do you mean twin engine inboards with the engines driving hydraulic pumps which then drive hydraulic motors? I don’t see any mention of saildrives...is that what you have?


The concept of hydraulic drive inboards has been around for years....Volvo Penta built and sold hydraulic drive packages over 40 years ago, as did others. They do have certain advantages, such as the ability to place the engine remotely from the drive pump and position weight where it’s most helpful. Not uncommon during the IOR rating days. Plus it does give you a ready made hydraulic system which could be used for windless power or maybe even a generator.

But, as mentioned by Skipper Pete, they also have disadvantages, most notably greater power transmission losses.

Whether there is a higher or lower degree of reliability, it seems to me, depends on the design of the system, and the maintenance it has had. Remember there are literally millions of hydraulically driven systems running around the country on all types of equipment, and the long term reliability is generally very good.

Perhaps a bit more exploration of the system is in order before rejecting it, particularly if the boat is a good fit for you.

DougR

[kjon38]

Good Day

The vessel has a Yanmar 27 HP 3GM30FC Freshwater cooled Diesel engine which powers the Hydraulic system for the two Volvo Hydraulic motors which turn the twin propeller shafts. The propellers are in front of the rudders,

Yanmar 27 HP Fresh water cooled Engine with 2050 Hours
Twin Volvo Hydraulic Motors for Dual props
Twin Stainless Steel Shafts with Dripless Stuffing Boxes

Trying to get some additional detail on the engine. Will post as soon as the owner gets back to me.

Thanks

Ken

[south4320]

Hi Ken
If you like the boat I wouldn't let the hydraulic system put you off. If done properly there is no reason why it should be high maintainence or have leaks. There are millions of hydraulic operated machines around the world operating reliably without leaks and reliability issues in hostile environments and subject to high shock loads.
Lots of people use hydraulics for steering and anchor winches. I have hydraulic furling which i haven't had a problem with.

As far as i know the biggest problem with hydraulics is the loss of efficiency. I'm not sure what the percentage is, i did some research on it some years ago but don't recall the figures.
However a single higher horsepower engine is more efficient than two lower horsepower engines so if the cat had two smaller horsepower engines they would also be less efficient. I don't know what the difference in efficiency is but it would be worthwhile researching it as there may not be a lot of difference from having one larger engine with hydraulic drive.

I would be having a good look at the hydraulic system, if a professional installation and there are no leaks and it is operating satisfactorily I wouldn't be put off it.

On the farm here we have numerous hydraulic equipment all operating reliably with minimal maintenance and no leaks apart from an old excavator which has done many thousands of hours work in tough conditions and does have some minor leaks.