Sail drives, how bad?

[jmschmidt]

These were a bad idea from the get-go. If you hit something even moderately hard make sure you have a water-tight bulkhead between the engine and the rest of the boat. Should have been restricted to racing boats.

[molly1]

Let me say this. I have been unable to use my yacht for 6 weeks and am unlikely to get it going within the next 3 months as ZF which makes all the drivers for Volvo and Yanmar cannot supply any parts for my SDD50 drive. I have a bent ( 2mm) prop shaft due to rope getting caught up. ZF says i have to buy a whole new sail drive $5500++ and they have none in stock and will have to wait while they make one.
I think this is a blatent lie as i cannot believe they would not have in stock considering the yacht is 5 years old.
The actual sail drive is a sd20.
I doubt I will ever buy a Beneteau or other brand that uses ZF DRIVES. This may be hard.
I currently have a Oceanis 55

[captnknopf]

I have had two cats with sail drives, one Volvo and one Yanmar. Had engine problems but no sail drive problems. I now have a Leopard with Yanmar engines with straight drives. Had the cone clutch go out on one transmission after 1500 hours. Have had cutless bearing problems but the engines are a dream. I was able to fix the cone clutches by rouging them up using valve grinding compound. I have put 500 hours on since the fix and it is working fine. Part of the reason I chose this cat was because of straight drives but it looses a stateroom because the straight drives take up so much room.

[Captain Bill]

Originally Posted by molly1

Let me say this. I have been unable to use my yacht for 6 weeks and am unlikely to get it going within the next 3 months as ZF which makes all the drivers for Volvo and Yanmar cannot supply any parts for my SDD50 drive. I have a bent ( 2mm) prop shaft due to rope getting caught up. ZF says i have to buy a whole new sail drive $5500++ and they have none in stock and will have to wait while they make one.
I think this is a blatent lie as i cannot believe they would not have in stock considering the yacht is 5 years old.
The actual sail drive is a sd20.
I doubt I will ever buy a Beneteau or other brand that uses ZF DRIVES. This may be hard.
I currently have a Oceanis 55

Your post is really confusing Do you have an SD50 or an SD20 drive. I don't believe that either one was produced by ZF. It is my understanding that the only Yanmar drive produced by ZF is the SD60. The only way to get a new shaft for and SD60 is to buy a whole lower unit which in fact costs more than an entire new drive. The SD20 on the other hand has been superseded by the SD25. It has been reported previously on the forum that the SD25 was a case design change only and all internal parts were interchangeable with the SD20. This is the same thing that Yanmar did with the jump from the SD40 the SD50. I have the parts manual for the SD40/SD50 and all of the internal parts are the same. If you truly have an SD20, it would seem that you can just buy the shaft for an SD25. Do you actually know what saildrive you have?

[valhalla360]

Originally Posted by a64pilot

I’m not so sure I buy either of those theories, and they are of course dependant on boat design. I measured my shaft angle and I believe it’s three degrees, which is negligible of course, and look at the pic to see how much drag my shaft has.
Attachment 198712

That massive overbuilt strut, I'm sure has a bit of drag to it. Seems like it runs almost 2/3 of the way to the bow.

Of course, not many boats with your style hull being built.

For a Cat or non-full keel mono, the shaft typically comes down at an sharper angle and has a strut or two to support the shaft.

That said, I'm not a fan of sail drives.

[Connemara]

Hmmm. I have saildrives on both boats (an OMC Zephyr and a Volvo Penta). Issues so far have involved the engine or transmission, respectively, but not the saildrive legs.

Two things:

1) A saildrive can be positioned so that the prop is at the centre of effort for the boat, while a shaft is most cases is astern of that point. Gotta be more efficient.

2) A number of people have worried that hitting something hard could lead to a massive hole in the boat, which is at first blush a a reasonable position. OTOH, when you hit something hard in the water it's usually because you've sailed into it and in that case the first thing that gets hits is the keel. (I speak from personal experience here ... slammed into a rock a few years ago at 5 knots, had a huge divot out of the keel, no impact on the saildrive leg.)



Connemara

[David B]

Originally Posted by stevensuf

I am considering a boat with saildrives, though having only ever had shafts I would really prefer shafts, but just how bad are sail drives?

I hear stories of constant problems, mostly expensive, I never had any issues with shaft drive and boxes, some say sail drives are not much of a problem, others report they are hell and considering i am talking probably 500 hours or more a year, just how much down time and costs are we looking at?

I know to avoid the yanmar sd40/50, any others that are particularly bad?

We have a 75HP Yanmar driving a ZF SPP Saildrive (the 360 degree rotating version of the ZF SD10). Our hull was treated with Coppercoat 8 years ago.

The drive (as with the hull) sees virtually no fouling - only a bit of slime.
I replace the cone anode on the prop (Flexofold 3-blade) every 2-3 years, and the ring anode on the drive every 3-4 years.

No corrosion on the drive - at all (we also have a galvanic isolator in circuit for protection at marinas).

Apart from changing the oil every couple of years (quick and easy job), the only service I have done was at the 6 year mark to strip the old epoxy coating off, down to the factory coating, re-coat with 4 coats of epoxy, then three coats of hard antifouling. This year we had a leak at the output shaft seal, so I need to replace those seals and for good measure, also the two tapered roller bearings (I have since been advised those shaft seals should be replaced every 5 years irrespective of service hours).

As for the rubber diaphragm, on Yanmars there are two of them, with a water sensor in between - that sensor is sometimes not connected to anything, so check that, but with two diaphragms, plus a sensor between them, I am happy (I would be nervous with only one as I am advised Volvo have).

As for damage, there is a big keel in front, and a big rudder behind - both much deeper than the saildrive, so unless I managed to reverse sideways onto a rock, I cannot see any issues, and the thing is very solid anyway.

Efficiency is greater than shaft drive as the thrust angle is correct. Typically the boat we have came with a 110HP in shaft drive version, and a 75HP in saildrive version. We easily achieve hull speed.

The engine is on rubber mounts, and the saildrive is fully isolated from the hull by those diaphragms - this means the only sound you hear is the engine noise, no transmitted noise through the hull.

With most manufacturers fitting saildrives these days, I suggest that should not be a decision point other than the type and condition.

Here is a link showing our saildrive and cone anode etc (which I did not change as I didn't have one that year), just after the new epoxy/antifoul treatmen as part of a Flexofold service.

https://www.youtube.com/watch?v=fConQRkPfMM&t=7s

Might be helpful in your decision making

I hope that helps.

David

[Neptune's Gear]

All systems need maintenance. There is a lot of poor quality information in this thread. Saildrives, if looked after, can be fine.
I had a volvo 120S, it did over 11,000 hours and 40,000 NM. Finally it was replaced because the engine was knackered. The service was simple, the rubber seal boot was only changed twice in 20 years. Still fine. A sail drive behind a keel should not be subject to many impacts....

[ausnp84]

Catamaran with two Lombardini saildrives and while they seem ok, I’ve seen the replacement bill the previous owner coughed up and once one fails, I’ll probably go down the Aussie cat route - rip out both engines and SD’s, and replace with two high thrust outboards in custom boxes on the transom. Less faf, six less holes in the boat, no more diesel fumes, and all that lovely storage space regained under the aft cabins, not to mention the colossal weight saving.

Add to that a diesel engine comes with a 3 year max warranty (give or take) whereas a new 30hp outboard has 7 years and less than half the price.

So back to the initial question. I prefer shaft drives but wouldn’t pass up a boat with SD’s if they’ve been well maintained, and if given the option, would go for outboards from the get-go.

N

[fritzthecat]

My personal experience is, that the same engines with SD50 on my previous catamaran used about 40% more diesel as the same engines on similar voyages in my new, bigger cat, with straight shafts consume.

[FuzzyFeat]

Sail drives are cheaper to install for the builder. The cost translates into maintenance expense for the owner.

My 37' cat had two french sail drives both needed work, both needed the diaphragm replaced. No parts available - not for love nor money. I was looking at 25 K minimum for replacement of one SD. Took them both out and replaced them with one 15 hp Honda 4 stroke The OB pivots in concert with the rudders. Excellent maneuverability. Never regretted my decision.
My previous boat had a straight shaft to a max prop. Twelve years of cruising - no problems. From what i see in in the boat yards, sail drives are a maintenance headache. I believe that if they were not cheaper for the builder and easier for the the designer they would not be used. Remember, if you are going to do some serious cruising, parts and and expertise can be in short supply in the backwaters of the world. Simple is better.

[Cayuse51]

Volvo D2-40 engines with Volvo 130S saildrives. More than 40,000 miles and once around the world and no problems other than maintenance to change the oil, zincs, and replacing the lower o-ring behind the prop.

[wannacat]

French sail drives? What make were they?

[Whosails]

We have a Wauquiez Gladiateur with saildrive. Installed in 2009. The yard it had been in before we bought it did something wrong and while the former owner was using it, it developed a serious problem. When we looked at it there were chewed up bolts in the locker. We insisted that it be fixed before we bought it. Moral of the story is that I would recommend using a qualified Volvo mechanic on these engines.

Also, it is recommended to use non copper bottom Paine on hulls that have these engines.

[FuzzyFeat]

The sail drives were branded as Nanni. The boat was 25 YO at the time. No parts for the transmission, No parts for the drive, no mechanic i spoke with, and there were many, ever heard of them. The transmissions were Borg Warner. Model discontinued and no parts or any information.



Manufactures have little incentive to keep repair parts after a model has been discontinued, so buyer beware.