Sail drive Vs Shaft drive on a sailboat

[Jim Schofield]

Looking at secondhand sailboats recently, most have shaft drive but a very few have retro-fitted saildrives.

Is one inherently better than the other ?

I'm thinking about the larger opening in the hull for a saildrive, is it more vulnerable ? Which is generally more efficient ? Easier to maintain ?

Do saildrives collect more lobster pots ?

Jim

 

[Tranona]

Looking at secondhand sailboats recently, most have shaft drive but a very few have retro-fitted saildrives.

Is one inherently better than the other ?

I'm thinking about the larger opening in the hull for a saildrive, is it more vulnerable ? Which is generally more efficient ? Easier to maintain ?

Do saildrives collect more lobster pots ?

Jim

You must be looking at old boats if the majority you are seeing are shaft drive. Equally very few boats are retrofitted with saildrive, although in the early days (1980's) some boats were offered with options.

Essentially the decision on which to fit is made at the design stage, so you will find that all Bavarias under 55' have saildrives, as do many HRs, all Hanses, but the fRench builders, Beneteau and Jeanneau use predominately shaft drives up until recently but most of their newer designs also have saildrives. the market is split between volvo and Yanmar, probably the majority in use are Volvo. There are a few fringe suppliers - Beta, Lombardini, Vetus, but few are fitted to volume selling boats.

The advantages of saildrive are partly packaging as the engine is more compact and there is more freedom about where you put it in today's flatter bottomed boats. Installations are generally smoother and quieter plus as the prop is usually further forward there is less prop walk effect. The thrust is parallel to the waterline so is arguably more efficient. No more vulnerable than conventional stern gear as they are usually just behind the keel, but it is still sensible to fit a rope cutter. Biggest downside is that they are very expensive to repair, or more likely replace if they do go wrong, and in theory the diaphragm should be replaced at 7 years at the cost typically of £1000. because the housings are aluminium you need to keep an eye on the anode, but newer examples have bigger anodes so they last longer. Basic maintenance pretty undemanding, but you need to check the oil regularly as water getting in means lower seals need replacing.

Remember than saildrives have been in use for over 30 years so are well proven. If buying a boat there are other much more important things to worry about. You rarely have a choice if you are fixed on a particular model of boat, so concentrate on choosing the right boat.

 

[Jim Schofield]

Thank you for the information, it is all old boats I'm looking at so I was surprised to find one with a saildrive. Have only seen pictures so far, so it's time to see it in the flesh !

Jim

 

[Tranona]

Thank you for the information, it is all old boats I'm looking at so I was surprised to find one with a saildrive. Have only seen pictures so far, so it's time to see it in the flesh !

Jim

Be wary of "old" saildrives - not necessarily because of the drive, but the old engines are becoming difficult to keep going and replacement is a pain - and expensive!

 

[Neeves]

Tranona, informative summary, many thanks.

I've never had a shaft drive, so have nothing to compare. But we have had no issues with our saildrives. In our cat one engine is behind the drive and the other in front - illustrating the flexibility that a saildrive offers, and underlining what you said. I note that in some new cats, for example Lagoon, the engines are now as far aft in the hulls as possible and there would simply be no room for a shaft (and rudders are now forward of the saildrive) - again emphasising the point you make of flexibility of location, compact (and maximising accommodation for yachts focussed at the charter market)

You mention that saildrives are expensive to repair and imply more so to replace (in comparison to what might be necessary for shaft drive) Do you know what the cost comparisons might be, roughly? Not having any experience of shaft drive (and having no problems with our saildrive) - is one more or less reliable than the other? - or are you simply unlucky if the saildrive goes wrong.

To add to your list, Bukh used to supply saildrives, we had one in our X-99, that's back in the late '80s early 90's. X-Yachts changed in the very early 90's, for the X-99, and I think went to Yanmar with saildrive.

Jonathan

 

[Tranona]

From bitter personal experience when saildrives go they "lunch" everything inside. The one on my old boat seized after 3500+ hours mainly as a charter boat in the Med. So lots of inexperienced people crashing backwards and forwards through the gears. All the bearings destroyed and oil laced with the debris. Nobody would repair it and a new drive I managed to get from a deal with a Volvo dealer. Cost £3000 installed. However Volvo will now in the UK only sell as spares and now cost over £4k. Better now to replace the whole engine and drive and sell the old engine. 8 hours labour to do the swap in most boats. Sometimes you can get used drives for about £1500. Fortunately such failures seem to be rare.

You are right about Bukh but they never made a huge number compared with Volvo at the time.

 

[jamesrichy]

See the Cruising World article on Saildrive maintenance June 26, 2017. You will avoid saildrives like the plague. They are great for the builder, as any warranty issues are entirely dealt with by the engine dealer, not the boat builder. But they are terrible for the boat owner. Huge costs for seals ($2500-$4000 every 5-7 years. Yanmar says replace the cones every 2000 hours ($4000), diving or hauling out every single year without fail, expensive zincs which are hard to find outside of major towns. Forget about getting a seal replaced in a small Mexican port. Cruising Worlds says a used boat with a saildrive is worth $10,000 less than the same boat with shaft drive.