# Sail drives vs shaft drives?



## yellowwducky (Nov 6, 2008)

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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## Omatako (Sep 14, 2003)

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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## sailingdog (Mar 19, 2006)

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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## yellowwducky (Nov 6, 2008)

Interesting, some of the points I have seen seem to highly go against them. Glad its not a universal problem type of installation.


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## sailingdog (Mar 19, 2006)

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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## tommays (Sep 9, 2008)

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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## Jeff_H (Feb 26, 2000)

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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## camaraderie (May 22, 2002)

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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## yellowwducky (Nov 6, 2008)

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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## camaraderie (May 22, 2002)

That's what you get for not looking at real sailboats!   
You could go for the electric Lagoon!


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## Jeff_H (Feb 26, 2000)

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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## mdidriksen (Aug 16, 2008)

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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## Giulietta (Nov 14, 2006)

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



Jeff_H said:


> 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*
> ...


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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## Giulietta (Nov 14, 2006)

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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## TSOJOURNER (Dec 16, 1999)

Looks like the AFLAC duck has his head stuck through the bottom of your boat! :laugher 

Mark


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## Giulietta (Nov 14, 2006)

citation34 said:


> Looks like the AFLAC duck has his head stuck through the bottom of your boat! :laugher
> 
> Mark


What do you mean??? What's an aflac??


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## Giulietta (Nov 14, 2006)

Forgot to tell you...
I now cover the saildrive with vaseline, and that stopped barnacles from growing..and the few that grow, come off real easy


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## RXBOT (Sep 7, 2007)

*Yamaha*

There is a saildrive made in Sweden using a motor based on 15hp Yamaha outboard. I have allways had good luck with Yamaha products. They say it's good up to 4000 kg boat.


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## doubleeboy (Jul 21, 2008)

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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## TSOJOURNER (Dec 16, 1999)

Giulietta said:


> What do you mean??? What's an aflac??


It's a comedic series of insurance ads that run here. Starring a funny duck. I thought your saildrive looked like a ducks head sticking through the hull. I didn't think about your not seeing the ads. Thinking is something I often miss....

Mark


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## yellowwducky (Nov 6, 2008)

If there is one thing I have learned so far, no one is going to be able to agree on what a 'real sailboat' is. Someone will like a Gunboat because its fast while someone else will point out it can't go to Antarctica. Someone else will point out that a Lagoon has more room than anything afloat while someone else will point out its slower than molasses.

If you can give me a universal definition of a 'real sailboat' I will give you a cookie! I like the Atlantic 48 and if I had to give up the cockpit the new Outremer 49 both look like 'real sailboats'.....to me. YMMV as they say.


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## smackdaddy (Aug 13, 2008)

I may not get the cookie...but it is pretty funny that you would be the first poster after the whole AFLAC thing.


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## yellowwducky (Nov 6, 2008)

Hehe, when I replied I didn't see the second page - these boards really need more posts on a single page.

Now, the thing I thought interesting - coating your saildrive in vaseline? Thats going to last what, a day? A week? Maybe the sonic growth inhibitors are the way to go in the future. Would sure be better than anti-fouling paint and vaseline I would think.


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## Giulietta (Nov 14, 2006)

yellowwducky said:


> Would sure be better than anti-fouling paint and vaseline I would think.


You would think..that's right.

Vaseline lasts over 4 months.


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## TSOJOURNER (Dec 16, 1999)

Ducy

go to user CP, then edit options, then you can select 40 posts per page.


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## tommays (Sep 9, 2008)

They grow pretty fast here  and it tough to get anything INSIDE the passages they grow in

They also jam the gears on folding props If you dont get down there and clean


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## Valiente (Jun 16, 2006)

I support Giu's case for his particular boat, on which I have sailed, and on which I have motored, perhaps a little more than I had hoped.

Now, here's a different pair of boats and a different pair of situations. I own two sailboats, a 1970s racer and a late 1980s full-keel steel cutter. Two more different monohulls would be hard to imagine, but they both have shaft drives.

On the racer, I went from a fixed two-blade 12 x 6 prop to an 11 x 8 two-blade folding Gori I bought used for $350 (they are usually quite expensive, like $1,000 plus at this size). I have to say I am very pleased with the results. Although I have lost a fraction of a knot at full throttle, I am able to go dead-slow _more slowly_ (from 2.7 to 1.5 knots), and this has meant I actually use the engine more instead of pointing at things and going into neutral. The biggest advantage is in sailing, however. Going to a folding prop seems to give me a half-knot of speed and the boat pretty well leaps forward when hit by a puff. It is very gratifying and the small hit on speed under power is completely worth it.

The steel cutter had a 18 x 13 three-blade in an aperture just behind the end of the full keel. I have purchased a 19 x 15 four-bladed, feathering Variprop with variable forward and reverse pitch, plus a universal coupler so that I can say goodbye to alignment problems, will isolate my transmission from shearing forces when shifting gears, and will more closely match my diesel's power band.

The feathering will increase my light-air perfomance, which is important to me, and the increased prop area should give me low-speed stopping power, which the cutter, having more windage to it than most boats, needs in close maneuvering.

The wet bilges issue is addressed with one of the usual bellows shaft seals.

Were I staying coastal, I probably wouldn't bother with this, but we intend to go offshore with this boat for some years.

So your own boat and pattern of use are going to dictate your choices here. As Giu points out, his easy access to haulouts, his fondness for speed and performance, and his essentially short-haul, coastal habits make the saildrive an easy choice. Even so, we both like the feathering/folding props. They really make a great difference in sailing ability, particularly in light airs.

About the only improvement in props I can see ever coming to recreational boats would be the AziPods that are on Coast Guard and some merchant ships. An AziPod with a folding prop would be near perfect; an AziPod that could retract _would _be perfect.

Azipod - Wikipedia, the free encyclopedia


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## Giulietta (Nov 14, 2006)

ehehehe

Val..look who makes the Azipod!!! ehehehehehehe


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## Valiente (Jun 16, 2006)

Yes, I thought you would enjoy that. My parents lived for many years one block from a manufacturing plant of theirs.


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## fred_hewitt (Oct 29, 2000)

I have been looking at Leopards for several years now, with a plan to buy one soon. As you all probably know, Moorings is a MAJOR buyer of these cats, and recently they went from a 47' with shaft drives to a 46' with saildrives. I was skeptical about such a major change, since Moorings has always touted the Leopards' skeg-mounted shaft drives as far superior to saildrives for the reasons mentioned in earlier posts.

At the show in Annapolis last fall, I was quite surprised by the increased usable volume of the 46. I believe this is a huge reason for going to saildrives. I also believe that Moorings is extremely careful about reliability and cost/ease/frequency of maintenance. 

I don't have a dog in this fight on behalf of either Leopard or Moorings, but as a potential Leopard buyer, I'll be looking to confirm my beliefs with Moorings before I buy.

Easy breezy,

Fred_Hewitt


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## 121Guy (May 6, 2007)

*Real space savings?*

I have had boats with inboard diesels with traditional shaft mounted props and now have a saildrive. Each have plusses and minuses. For a boat that would stay in the water cruising for a long time, I believe the shaft and strut and prop are the way to go. For the performance boat that comes out of the water often, the saildrive may be superior. In either case, the engine and transmission take up roughly the same amount of room. Some boats are offered with either option. I do not believe that a properly designed traditional installation will take up any more considerable room that a saildrive. Look at the Beneteau and Catalina and Hunter boats. All the cruisers still use traditional installations while trying to maximize interior volume. I have not operated a large catamaran with saildrives but have operated a large power cruiser with twin traditional shafts as well as a large catamaran with twin traditional shafts. I cannot see how the low speed docking and manuevering control of each might be improved with a saildrive, but perhaps they can. I do believe that the saildrive provides better low speed manueverability in a single engine monohull though. Last, I believe that the three factors driving the saildrive choice are that they present less drag that traditional strut and shaft installations, that the saildrive can be placed in an optimal location as far as weight and distance from rudder is concerned and that they are so much easier to install than a shaft and strut on a new build that they provide a considerable savings to the builder in both materials and labor.

Good luck,

121 Guy


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## Valiente (Jun 16, 2006)

An argument in favour of the saildrive is the ability to put the engine nearer the CG of a monohull, but I don't see many models that do this, nor would it be a huge advantage over putting a traditional engine right over the keel and running a shaft at a shallower angle out the back.

People have fairly fixed ideas about how they expect saloons to look, and even a low box in the middle of a saloon isn't going to find a big fan base, no matter how logical it is in terms of keeping weight out of the ends of the boat.

It may have been an Ericson or one of the old Wanderers owned by the Hiscocks in the '60s, but I recall one boat where the presence of a fully insulated engine box didn't impede getting around in the boat, and the full access made up for it. I also recall dimly one boat with an engine mounted in the saloon that ran some sort of hot water tubing that turned the box into a sort of ceramic Dutch oven affair that kept the cabin warm when the engine was on.


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## Rockter (Sep 11, 2006)

There is not a sailldrive under the sun that will work with a long keel double-ender, so for me, it's orthodox propshaft every time.

I can get to the gearbox in an instant, I can check its temperature, I can see a gearbox oil leak promptly, and I can change the gearbox oil in about 20 minutes, and I can take the gearbox right off there in about 2 hours ( I had to do that about 5 times before I finally got to the reason why it was leaking)... all of those points begin to matter on an older motor.

And I like watching a propshaft spin.

Engine alignment takes longer though. Saildrive doesn't have to worry about that one much.

Rockter.
.


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## Valiente (Jun 16, 2006)

Re: alignment. Get soft mounts for your engine and a universal joint coupler and your alignment problems (along with stresses the gearbox with gear shifting) is a thing of the past as the thrust bearing takes "the shock" and not the transmission.

A drive saver disc or two helps here, but doesn't solve alignment issues, particularly running the engine at angles of heel.


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## mdidriksen (Aug 16, 2008)

Valiente said:


> An argument in favour of the saildrive is the ability to put the engine nearer the CG of a monohull, but I don't see many models that do this, nor would it be a huge advantage over putting a traditional engine right over the keel and running a shaft at a shallower angle out the back.


Interestingly, this is exactly what I am moving away from with my saildrive conversion. The boat is a late CCA/early IOR influenced old ocean racer/cruiser, and the original design had a shaft drive sitting right on top of the keel. Great for performance, but takes up half the salon (boat is only 34 feet).

While putting a traditional shaftdrive under the companionway steps is an option, I'd be a bit worried about performance under power, given the need to have a pretty steep angle on the shaft and the fact that the prop would end up quite close to the skeg hung rudder. Couple that with the fact that I'll be hauling out every winter and my usage will be more like daysailing and weekending, and it became a pretty easy decision to go with the saildrive.


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## Valiente (Jun 16, 2006)

If it's daysailing and weekending, why not save money and space and just have an outboard on the back?

No, I'm not joking! Conversely, you could have a fibreglass well built and drop an outboard in there for more protection and less weight off the end.

People used to scull boats up to the high 30s in length with 14 foot sweeps...but perhaps this is too much economy for the modern cruiser.

The rule of thumb for engines, shafts and prop clearance is 14-15 degrees of "tilt" and the prop needs 10% of its diameter in clearance from the hull.

I have a pretty similar boat, and for all its wonderful attributes in my mind, cutting a hole in the hull to drop in a new diesel saildrive would cost more than it is worth. But if you love the boat so much that you expect to have it 25 more years and never expect to recoup the cost of conversion, then it's not going to bug you.


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## Giulietta (Nov 14, 2006)

Off course, if I was dragging a 20.000lb long keel, and had a rudder behind all kinds of gimmicks, I wouldn't bother with a saildrive..

I'd be more concerned with other things to make the boat move by force of wind...such as sails, mast etc...the drag caused by a shaft wouldn't worry me...

Now...

LOOK BELLOW...look at the drag signature on this!!!

Tell me..look at the profile from the front..look at the minimal size, look at the cleanliness of the lines..and tell me..if you were really concerned with making the boat move by sailing...wouldn't you want a puppy like this saildrive???

Be honest!! Wouldn't you??


















Different purposes with different systems

.


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## camaraderie (May 22, 2002)

Well...the sail drive makes sense but you need to get rid of that big shark looking thing...that has GOT to create a lot of drag!


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## sailingdog (Mar 19, 2006)

He did...the most recent photos have a plain white, boring, bulb....he thinks the shark was scaring off the dolphins...


camaraderie said:


> Well...the sail drive makes sense but you need to get rid of that big shark looking thing...that has GOT to create a lot of drag!


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## mdidriksen (Aug 16, 2008)

Valiente said:


> If it's daysailing and weekending, why not save money and space and just have an outboard on the back?


Daysailing and weekending are the immediate future, but the boat was built for offshore. An outboard is not an option in my view for this particular boat and for my future (hopefully) usage.



Valiente said:


> I have a pretty similar boat, and for all its wonderful attributes in my mind, cutting a hole in the hull to drop in a new diesel saildrive would cost more than it is worth. But if you love the boat so much that you expect to have it 25 more years and never expect to recoup the cost of conversion, then it's not going to bug you.


Who said the cost doesn't bug me???  That being said, 90% of the cost is for the engine itself and would have been incurred for a shaft drive as well. Installation of the saildrive is actually pretty easy.


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