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Discussion Starter · #1 · (Edited)
Hi all,

I keep seeing the vast majority of boats equiped with 'saildrives'. I have not really been able to figure out the difference between a saildrive and a shaft drive other than seeing that shaft drives are apparently 'better'. What exactly is the difference - props are obviously connected to a diesel engine via one of these two methods I assume but if shaft drives are indeed 'better' why do I not read more about them. It seems almost all boats I have seen mention saildrives.

Does it impact the prop location? Higher/lower? Does it impact weight? About all I know about shaft drives was that my old Yamaha motorcycle had one and that shaft drives on a motorbike were more reliable than chains.

Thanks and regards for any thoughts or good links!

edit...

I kept digging around I came across comments comparing a couple boats and this person mentioned the following......

"stay very very far away from anything with a saildrive" was the opinion and went on to describe that saildrives are aluminum housed below the boat immersed in seawater which, when it fails requires hauling the boat. They are easier to build and leave more room inside as well as gets an engine out of an aft bunk (or two in a cat). I gather from the comment that shaft drives though ar easier to fix, less likely to break and don't expose a prop as much (although don't go snorkeling near the back of the boat maybe or you might get sliced up??).
 

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A saildrive is a little like having an outboard leg sticking out the bottom of the boat and connected to an engine inside the boat.

The first thing that I reckon you have wrong (but will stand corrected) is that saildrives dominate. I think shaft drives are far more prolific.

One advantage of a saildrive is that the ones I have seen are totally watertight and the boat has a totally dry bilge whereas shafts mostly leaks a little water.
 

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The big disadvantage is that when you have a problem with the saildrive and have to pull it, you will have a huge hole in the bottom of your boat. A properly installed saildrive is a good thing, a badly installed one or a defective one is a nightmare.

Saildrives tend to have far less propwalk, since the saildrive is installed with the prop basically vertical... They don't have the same alignment issues that you get with shaft-drives. However, they're generally found on more modern designs—I've never seen a full-keel boat with a saildrive. :)
 

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OMC made a saildrive that gave all saildrives a huge black eye for many years. :) Yanmar has had a few problems with theirs that haven't helped saildrives out much recently as well. :)
 

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It also depends on were you live in this area Barnacle growth is a problem on units that have there water intake in the leg because you cant really paint inside the intake grates

Up here most boats are only in the water 6 months or so and this makes it pretty easy to stay on top of them BUT in areas were poeple may stay in for 2 years between hauls things like drive oil changes become and issue
 

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Farr 11.6 (Farr 38)
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I have lived with both a saildrives and conventional prop shafts and I would say that the comparason from my experience is that Saildrives offer the following advantages:
  • Easier for manufacturers to install accurately but not necessarily less expensive.
  • Less maintenance in the short run
  • higher fuel efficiency
  • Less drag
  • No water in the bilge to deal with
  • Do not have shaft alignment, coupling and packing gland issues to deal with.
  • Easier to isolate for less vibration and quieter operation
The disadvantages:
  • Way more prop walk
  • proprietory propellors
  • need more expensive geared folding or feathering props if low drag prop is used
  • need to haul boat for almost any form of gearbox maintenance including changing lube oil
  • big hole in the bottom of the boat
  • Need special non-copper type bottom paints
  • expensive proprietary zincs that need frequent attention
Some of the old problems with saildrives have been addressed by some manufacturers. Saildrives used to have water passages for cooling water or exhaust like an outboard motor. These passages meant that sooner or later the coatings would flake loose and sooner or later spell the end of the life for the lower unit casings. Today some manufacturers have changed the design of their saildrives to eliminate the water passages. This is a plus in all ways.

The metalergy of saildrives have improved. Early saildrives used aluminum alloys that seemed especially prone to electrolysis and other forms of corrosion problems. I understand that some sail drive manufacturers are now using much better corrosion resistant alloys.

Jeff
 

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I agree entirely with what Jeff has said but would note that there is still an open question about the reliability of even today's saildrives. OMC's did have a lot of problems but some will recall the lawsuit Gavin Stener has in progress against BOTH Yanmar and Tartan for the deterioration of 2 saildrives. This is supported by Tartan's refusal to pay Yanmar and the switch to Volvo drives and the CLAIM of many customer problems with Yanmar drives (NOTE: the claim was UNSUPPORTED in the recent MackBoring/Yanmar NJ court case). Mr. Stener's case will go to trial next month if there are not further delays and we shall see whether the claims are supported by facts and a favorable court decision.
Assuming one wishes to avoid Yanmar pending the outcome...this leave you with the sole choice of Volvo for a sail drive and that is one company whose reputation for low product support and high repair and parts costs in marine engines is well known.

Finally...if one is planning on cruising to distant shores I think it would be a very poor decision to buy a saildrive from anyone. Everything is proprietary, and finding someone qualified to make repairs can be extremely difficult and parts can take a long time to arrive and make it through customs. Someone can always fix a standard diesel/shaft no matter where you go.

Saildrives have their advantages as Jeff enumerates...but if I were not engaged in racing or coastal cruising in 1st world countries, I would avoid them entirely.
 

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Discussion Starter · #9 ·
I am not sure you will get the choice though camaraderie,

'Hello, Lagoon/Foutaine/Manta/Leopard/xxxxxx, I don't want a saildrive, can you please re-engineer your boat so mine can have a shaft drive'

'click'

I could be mistaken of course but it seems its not as simple a decision as microwave or no microwave.
 

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Farr 11.6 (Farr 38)
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Camaraderie is exactly right, my last paragraph should have read "The metalergy of some saildrives have improved. Early saildrives used aluminum alloys that seemed especially prone to electrolysis and other forms of corrosion problems. I understand that some sail drive manufacturers are now using much better corrosion resistant alloys."

I also want to point out that Buhk makes very nice engines and saildrives. My only gripe with some of their models is that you must use GORI props and I found the Gori's to be short-lived with terrible factory support.

Jeff
 

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Jeff H:

Curious what you mean regarding the need for more expensive or proprietary props?

I'm in the midst of installing a Yanmar saildrive and from what I can tell there is no difference in cost for the prop I plan on installing (Flex O Fold 2 Blade) compared to a shaft drive. It may be that due to my desire for a lower drag folding prop I've removed myself from the issue you are raising, but in the course of researching engines I hadn't come across this issue before.

Thanks,

MD
 

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I, as many may know here, had both, and have a saildrive.

Ture the saildrive tech has come a long way, nowadays, I wouldn't have it any other way.

Just for the record, and with regards to Yanmar, I did have a problem with my saildrive, that Yanmar, admited, and replaced the whole unit for free, and geve me a reset on the warranty. The problem had to do with the material, and paint, and we leave it at that..they honored the deal, and I recommend them.

I added an extra zinc that I remove when sailing that is connected to the engine, just as an extra precaution.

Anyway...Jeff..allow me to disagree...where I disagree in blue

I have lived with both a saildrives and conventional prop shafts and I would say that the comparason from my experience is that Saildrives offer the following advantages:
  • Easier for manufacturers to install accurately but not necessarily less expensive. Disagree, it's not easy to install when new...I know that
  • Less maintenance in the short run True
  • higher fuel efficiency True
  • Less drag YES!!! TRUE
  • No water in the bilge to deal with true
  • Do not have shaft alignment, coupling and packing gland issues to deal with.
  • Easier to isolate for less vibration and quieter operation
The disadvantages:
  • Way more prop walk Not entirely true, the saildrive can be installed lower and further from the rudder
  • proprietory propellors Not true..you can get SD props from pretty much anyone now
  • need more expensive geared folding or feathering props if low drag prop is used Sorry..not true..I have the Gori which costs the same where it is installed
  • need to haul boat for almost any form of gearbox maintenance including changing lube oil True
  • big hole in the bottom of the boat, and the shaft is not a whole too??
  • Need special non-copper type bottom paints True
  • expensive proprietary zincs that need frequent attention
Not that expensive really a set of zincs now for $35.00 from Yanmar

Some of the old problems with saildrives have been addressed by some manufacturers. Saildrives used to have water passages for cooling water or exhaust like an outboard motor. These passages meant that sooner or later the coatings would flake loose and sooner or later spell the end of the life for the lower unit casings. Today some manufacturers have changed the design of their saildrives to eliminate the water passages. This is a plus in all ways.

The metalergy of saildrives have improved. Early saildrives used aluminum alloys that seemed especially prone to electrolysis and other forms of corrosion problems. I understand that some sail drive manufacturers are now using much better corrosion resistant alloys. YES!!!!

Jeff
Now...If I was going to cruise the World..maybe I use a shaft for ease of maintenace in weird Countries...

I am performance oriented, have a SD50 racing saildrive, and it's the best thing I ever had...

Would I have a shaft?? NEVER AGAIN!!

Now..Volvo Vs Yanmar..let's say I could have a Volvo..but for me..NEVER AGAIN
 

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OK..Now my opinion on one versus the other one..

I sail coastal and need speed, therefore a shaft was out of the question...

When I decided on the engine, Yanmar, VW, and Volvo, I knew I wanted nothing from Volvo, (bad previous expereinces), so ut was VW, a new engine no one knew about it or Yanmar..

Yanmar is probably, not, actually is, the best marine engine in the market today. So Yanmar it was.

Now for the propulsion.

I really gave it a lot of thought and opted for the saildrive, for performance reasons..I am glad I did.

The boat does 9kts on engine, and does not vibrate, has no need for thru hulls (which add drag), and weird valves, and is quite fuel efficient.

I have the extra thin profile SD, the SD 50, the normal one is the SD40, mine is also longer.

The maintenance is none, change the transmission oil when the boat is on the hard, not a big deal, since my boat comes off 3 or 4 times a year, but you can go 2 or 3 years on one oil set. Its like that valvoline stuff.

The SD actually does not need any paint other than the factory one, altough I decided to paint mine, to add extra protection, and now, the zincs can be cahnged withou removing the prop, as Yanmar came upo with a 2 halve system.

So a few minutes under water and you replace the zincs..no problem.

The saildrive is installed in a special ring built into the boat, and the whole has a rubber gasket, with a leak alarm. even if the gasket tears, very unlikely, the gap is so small any pump will remove the water.

The saildrive has a valve that cuts the raw water intake, so you can change the impellers at sea.

The saildrive has another advantage, it does not require water intake filters, hence if you sail in dirty waters, that is another peace of mind..
and it does not requirer any other changes.

The truth is there are a lot of naysayers, but normally they hear say, and tell..they know not much..and as with all new ideas, there is allways opinion against from the ignorant...

Now...why I have one...I sail coastal, and need the performance..that is why I have it...would I have it on an old shoe??? NO..they can't go on old shoes...

Would I have it on a boat to go around the World?? NO..not because of technical problems, but because you may not find spares in Guatemala..or Morocco....but the chances of anything wrong with a saildrive are so thin..I might consider it..

So my advice to you..GET IT!! no questions asked...

 

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Hi Alex, Aflac is a USA insurance company that does TV commercials using a duck which is pretty humorous.

michael

btw, gonna close on the Dehler 39 real quick, saildrive and all, thanks for your encouragement.
 
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