Jump to content

Sail drive vs inline drive


Recommended Posts

I am researching my next boat, to cruise on and live part time. 40 or more feet. Most boats have inline shafts but there are sail drives too. What are the pros and cons of each and which is better to you?

 

Link to post
Share on other sites

Sail drive has less vibration, a little bit less drag, a better drive line angle. It also has a mix of metals with salt water flowing thru them, leading to possible large electrolysis damage. Shaft seals can leak. Most repairs are involved & expensive. Builders love them because they are so easy to install & take less space. Two extra 90 degree gear sets rob power. Large circle of rubber tasked with keeping water out. Barnacle growth inside leg problematic to deal with.

 

Shaft drives are old school tech & repairable anywhere in the world. No aluminum metal anywhere, all bronze & stainless steel, any electrolysis issues take yrs to become a problem.  Alignment must be established & maintained. Takes more space from the interior, more vibration (in most cases). If shaft water gland fails leakage is easily stopped & low volume.

 

Link to post
Share on other sites

Builders love sail drive because no alignment required.

Experienced long distance sailors tend to like shaft drives because easy to fix with a lathe and a hammer.

However, you will have a hard time finding a production mass market boat in the last 20 years without a sail drive.

Link to post
Share on other sites
2 hours ago, longy said:

Sail drive has less vibration, a little bit less drag ...

Sail drive is not necessarily less drag, the serious racing boats have a shaft drive that is faired.

Link to post
Share on other sites
6 hours ago, longy said:

Sail drive has less vibration, a little bit less drag, a better drive line angle. It also has a mix of metals with salt water flowing thru them, leading to possible large electrolysis damage. Shaft seals can leak. Most repairs are involved & expensive. Builders love them because they are so easy to install & take less space. Two extra 90 degree gear sets rob power. Large circle of rubber tasked with keeping water out. Barnacle growth inside leg problematic to deal with.

 

Shaft drives are old school tech & repairable anywhere in the world. No aluminum metal anywhere, all bronze & stainless steel, any electrolysis issues take yrs to become a problem.  Alignment must be established & maintained. Takes more space from the interior, more vibration (in most cases). If shaft water gland fails leakage is easily stopped & low volume.

 

I would say Longy has pretty well summed it up. FRANCIS LEE has a sail drive and I like it. My dive service makes sure the zincs are always fresh.

Link to post
Share on other sites

Re the barnacles: I have heard of people filling the cooling water passage in a sail drive with epoxy and using an ordinary thru-hull for the engine water inlet.

My shaft drive system is 48 years old. I got a new cutless bearing while getting the shaft replaced, hitting a log bent it. That is about it for nearly 5 decades except zincs and a new carbon seal. I am pretty sure that is an order of magnitude less maintenance than a sail drive would be over that time span. The boat was still usable after hitting the log, it just had an annoying vibration. The consequences of that with a sail drive could possibly have been considerably worse.

OTOH a sail drive is more efficient and quieter. The bigger prop at a better angle makes up for gearing losses and then some.

 

 

Link to post
Share on other sites

Not much to add to Longy.  The cost availability of repair would be a big consideration for cruising but they are all over and in every cat and new mono. I know of three in the last two months that have flooded. There might be some saildrives that are better than others.  

Link to post
Share on other sites

I'd prefer shaft drive over sail drive on a used boat that I would keep for many years.     But I might take a sail drive over a shaft drive that has an almost unreachable stuffing box.

Link to post
Share on other sites
2 hours ago, kent_island_sailor said:

Re the barnacles: I have heard of people filling the cooling water passage in a sail drive with epoxy and using an ordinary thru-hull for the engine water inlet.

We did this to mine when it was new. In addition to keeping the barnacles out, it now corrodes only from the outside in, rather than also from the inside out. 

Having owned both: two identical boats in identical condition, I'd take the shaft drive. Any significant difference in them, I'd let those differences decide, rather than the drive type. 

It isn't just ease of install, my boat was custom built, could have had whatever I wanted. But the plan dictated either a saildrive or a V-drive, and I took the saildrive over the V drive (with stuffing box under the engine/trans). The position of the engine often paints you into a corner. 

Link to post
Share on other sites
8 hours ago, kent_island_sailor said:

OTOH a sail drive is more efficient and quieter. The bigger prop at a better angle makes up for gearing losses and then some.

What? There's no way you can put a bigger prop on a sail drive than a shaft, unless the shaft is at some really weird shallow angle to the hull. And that's on the designer/builder. And I don't think a sail drive offers the same range of choice WRT reduction ratios meaning you have to spin a smaller prop faster. I have a 3:1 reduction pushing a 22" adjustable pitch/feathering prop.

I don't really care one way or the other which someone chooses, FWIW. Sail drives are a lot more complicated mechanically but installation/alignment isn't much of an issue. Access to maintenance - once again back on the designer/builder, if they don't think it's important, it's on you to decide what your response will be.

FKT

Link to post
Share on other sites

Currently I have one of each, both are a PITA in their own way.

The Adams came with a Volvo motor and sail drive, not a fan of either but both still going fine after ten years. Helps to have a spare motor and a couple of saildrives in the shed, just to make sure I don’t ever need them...

The boat is so sweet I was prepared to put up with the VP stuff.

OTOH the Valiant has my preferred setup, a Yanmar and a shaft drive. Unfortunately it has a V drive and an inaccessible stern gland. Paradoxically I think it would be better off with a saildrive and a motor round the right way.

Neither are a big deal in reality, it’s just a maintenance issue.

Link to post
Share on other sites
8 hours ago, olaf hart said:

Unfortunately it has a V drive and an inaccessible stern gland.

I had to google "V drive"...

Do you know what was the thinking behind choosing this configuration on a sailing boat ? I know that there are other considerations especially on a cruising boat but normally you would want the engine as close to the centre of the boat as possible to optimise comfort and speed at sea!

Link to post
Share on other sites
9 minutes ago, Panoramix said:

I had to google "V drive"...

Do you know what was the thinking behind choosing this configuration on a sailing boat ? I know that there are other considerations especially on a cruising boat but normally you would want the engine as close to the centre of the boat as possible to optimise comfort and speed at sea!

Living space.

Personally I'd never willingly own a boat where essential maintenance was severely compromised in such a fashion but that's me - I fix my own stuff so pay attention to such things.

You can guarantee that if something is very hard to access that it hasn't been regularly serviced. 

FKT

Link to post
Share on other sites
7 minutes ago, Fah Kiew Tu said:

Living space.

Personally I'd never willingly own a boat where essential maintenance was severely compromised in such a fashion but that's me - I fix my own stuff so pay attention to such things.

You can guarantee that if something is very hard to access that it hasn't been regularly serviced. 

FKT

OK, I should have thought about this, so designing boats to stay in marinas is not such a novelty!

It is also a safety issue as if something goes horribly wrong with the shaft, you want to be able to stuff rags there PDQ!

Link to post
Share on other sites

In this case the stern gland was replaced recently and a double seal Vetus type of gland installed.

it is grease filled and has a remote filler tube with a zirc fitting, so I can fill the gland with grease and feel if it is dripping under the gearbox.

but you are right, I plan to replace it with a dripless bearing or a Volvoseal on a shorter length of hose, so I can see and inspect it. ATM it’s inside the tunnel through the gearbox, the rubber hose length is too long.

I suspect that might mean there is some old scoring on the shaft aft of the gland, so there may be a new shaft in the equation as well...

Link to post
Share on other sites
1 hour ago, olaf hart said:

In this case the stern gland was replaced recently and a double seal Vetus type of gland installed.

it is grease filled and has a remote filler tube with a zirc fitting, so I can fill the gland with grease and feel if it is dripping under the gearbox.

but you are right, I plan to replace it with a dripless bearing or a Volvoseal on a shorter length of hose, so I can see and inspect it. ATM it’s inside the tunnel through the gearbox, the rubber hose length is too long.

I suspect that might mean there is some old scoring on the shaft aft of the gland, so there may be a new shaft in the equation as well...

If you do need a new shaft and get an outrageous quote, feel free to come & talk to me about it. I have a taper turning attachment on my big lathe, made my own prop shaft, regularly turn Morse tapers for milling machine tooling etc.

I expect to haul out in 2-3 weeks and have a leaking lip seal so am going to be stripping down my prop, shaft, outer bushing, inner thrust assembly etc for replacement seals and new upgraded parts. PITA but - shrug. All relatively easily accessible. I'm going to fit an auto-dispensing pressurised grease reservoir so as to keep the shaft tunnel under positive head pressure.

FKT

Link to post
Share on other sites
41 minutes ago, Fah Kiew Tu said:

If you do need a new shaft and get an outrageous quote, feel free to come & talk to me about it. I have a taper turning attachment on my big lathe, made my own prop shaft, regularly turn Morse tapers for milling machine tooling etc.

I expect to haul out in 2-3 weeks and have a leaking lip seal so am going to be stripping down my prop, shaft, outer bushing, inner thrust assembly etc for replacement seals and new upgraded parts. PITA but - shrug. All relatively easily accessible. I'm going to fit an auto-dispensing pressurised grease reservoir so as to keep the shaft tunnel under positive head pressure.

FKT

When I bought the Valiant the grease in the gland was the regular blue marine stuff. Over time it hardened and the seal leaked, I could feel small hard blue crystals on the shaft after a run.

so I did some research and moved to white water pump grease, it is much more effective, doesn’t seem to harden, and keeps the boat dry when it is not being used.

It is also much easier to pump into the gland.

  • Like 1
Link to post
Share on other sites
6 minutes ago, Max Rockatansky said:

Every time I see one of these threads I chuckle, thinking about my 30-year-old saildrives and dry bilges

Yep, they have a lot going for them, just keep up the maintenance.
Where I live it’s no problem to haul the boat at least once a year, which seems to be a reasonable interval for a saildrive.

over ten years the only issues have been replacing the lower unit seal, I had no problems removing and replacing the lower unit gears and shaft and just asked the VP guy replace the seal.

the other one was a loose ring anode, again the VP guy told me he puts loctite on the anode screws.

 

Link to post
Share on other sites
58 minutes ago, Max Rockatansky said:

Every time I see one of these threads I chuckle, thinking about my 30-year-old saildrives and dry bilges

My bilge would be almost dry except for the keel stepped mast.   It lets in far, far more water than my prop shaft does.

Link to post
Share on other sites
2 hours ago, Max Rockatansky said:

Every time I see one of these threads I chuckle, thinking about my 30-year-old saildrives and dry bilges

It's worth pointing out, in many instances, specifically marine, what was made 30 years ago may be a touch higher quality then what comes off the production line today.......

Link to post
Share on other sites
2 hours ago, Max Rockatansky said:

Every time I see one of these threads I chuckle, thinking about my 30-year-old saildrives and dry bilges

With modern seals, a shaft can be as dry as a saildrive. There is a (vanishingly) small possibility of the seal failing and flooding the boat, but no more risk than a saildrive boot failing and doing same.

Link to post
Share on other sites
49 minutes ago, DDW said:

With modern seals, a shaft can be as dry as a saildrive. There is a (vanishingly) small possibility of the seal failing and flooding the boat, but no more risk than a saildrive boot failing and doing same.

Before salt water gets in the boat through a saildrive there are 2 seals and an alarm letting you know when the first seal stops being functional... so not sure which one is better or worse.

As electric becomes more common, I wonder if we will see "rudder drives" appear (electric drive attached to the rudder). That would be good, super manoeuvrable boat, one less hole in the hull and if you mount it on the stern, no hole in the hull at all for engine + rudder! Hanse experimented with something like this a few years ago but it didn't catch... may be next time!

Link to post
Share on other sites
7 hours ago, Panoramix said:

I had to google "V drive"...

Do you know what was the thinking behind choosing this configuration on a sailing boat ? I know that there are other considerations especially on a cruising boat but normally you would want the engine as close to the centre of the boat as possible to optimise comfort and speed at sea!

The IOR handicap rule favored engines aft - but also rewarded props forward. Viola! a V-drive install! Or hydraulic drive to achieve the same thing

Link to post
Share on other sites

Lot's of good info here so far, I will add a few details. The paint on saildrives is different as it must be compatible with aluminum. Usual bottom paint will eat the drive. In my area it does not seem to last as long as typical bottom paint. Anodes on my volvo last a very long time, but are unique and hard to get. So far they can only be ordered from volvo which makes me nervous as they do not have a great reputation of suporting legacy products. If you have a large failure of the drive it must be removed completely for service. This has to be done out of the water, with the engine often needing to be moved forward to get clearence to remove the drive.  I know this can also be true of shaft drives, but with a saildrive there are a lot more parts below the waterline outside the boat to go bad. This is not theoredical, my 9 year old boat has had the drive out twice.

The saildrive holds the prop vertical, so backing is more predictable. They work great with folding props.

Having owned both types, my next boat will have a shaft drive.

 

Link to post
Share on other sites
1 minute ago, longy said:

The IOR handicap rule favored engines aft - but also rewarded props forward. Viola! a V-drive install! Or hydraulic drive to achieve the same thing

Is there any seaworthy feature the IOR rule didn't try to tamper ?

Link to post
Share on other sites

I don't know why the rule liked props forward, but centering the engine weight over the keel would be a large benefit. So it was penalized..

Link to post
Share on other sites
5 hours ago, SASSAFRASS said:

Are sail drives apples to apples or is there a significant difference between brands? Seems like lots of Yanmar and some Volvo any others?

Volvo have a good rep for saildrives, not for motors.

Yanmar have a good rep for motors, not for saildrives, they had some seal problems in their early models.

There is a UK company, makes stand alone drives, and I think Beta use them as well. There was also a Bukh saildrive, no further comment.

Seems to me it’s the devils choice, once you have picked your saildrive they have you trapped for life...

Link to post
Share on other sites

Interesting I guess there are only OEM mating options. Kubota engine on a volvo drive sounds like a winner. Beta was probably repacking one wonder if it was the Volvo.

Link to post
Share on other sites

 Beta use something called a Technodrive sea prop 60, but also make adaptors for Volvo, Bukh and Yanmar sail drives.

So I guess that would be a Kubota Volvo adaptor..

Link to post
Share on other sites

There is another option, the one I chose.

At the moment it’s raining used VP120 saildrives, as people re engine and install VP 130s with their new engines.

I have two in my shed at the moment, one with a damaged cone, and regularly knock more back.

I also picked up a low hours VP 2030 from a mate who was heading to the pacific and re engined, which is a direct drop in replacement for my existing VP2003.

The VP 2030 is a nice efficient mechanical injection Perkins engine, probably the best VP motor made, with lots of spares in tractor shops around the world.

The other advantage is both the motor and saildrive are direct replacements on my existing engine bed, so this appears to be the sweet spot.

  • Like 1
Link to post
Share on other sites
Just now, olaf hart said:

There is another option, the one I chose.

At the moment it’s raining used VP120 saildrives, as people re engine and install VP 130s with their new engines.

I have two in my shed at the moment, one with a damaged cone, and regularly knock more back.

I also picked up a low hours VP 2030 from a mate who was heading to the pacific and re engined, which is a direct drop in replacement for my existing VP2003.

The VP 2030 is a nice efficient mechanical injection Perkins engine, probably the best VP motor made, with lots of spares in tractor shops around the world.

The other advantage is both the motor and saildrive are direct replacements on my existing engine bed, so this appears to be the sweet spot.

There's 2 for sale on Gumtree ATM over in the Huon... unless you've bought them already.

Funny thing I'm thinking of building a barge and have toyed with the idea of using saildrives on it. I must have a chat with you about this at some point.

FKT

Link to post
Share on other sites
12 hours ago, Panoramix said:

Before salt water gets in the boat through a saildrive there are 2 seals and an alarm letting you know when the first seal stops being functional... so not sure which one is better or worse.

Only on the Yanmar, not on Volvo (or at least some Volvos). My Volvo D2-75 has a single boot and no sensor.

There are more than a couple of saildrive manufacturers. My aforementioned Volvo has very little on it manufactured by Volvo - the engine says Perkins/Catapillar in the casting but is actually a Shibaura (IHI), the saildrive is manufactured by ZF/Hirth. I think the label on the top might be made by Volvo and perhaps the shade of green paint. Many of the engine parts can be purchased from a local New Holland tractor dealer.

Lots of people make anodes for saildrives, I can pick from several for my Volvo/ZF/Hirth. 

Link to post
Share on other sites
15 hours ago, longy said:

I don't know why the rule liked props forward, but centering the engine weight over the keel would be a large benefit. So it was penalized..

I don't think there was anything in the rule favoring prop being fwd if my aging memory isn't failing, but I could be remembering incorrectly.  The trend was to have the prop tucked right behind the keel to reduce drag.

Link to post
Share on other sites
On 4/4/2021 at 1:31 AM, Panoramix said:

I had to google "V drive"...

Do you know what was the thinking behind choosing this configuration on a sailing boat ? I know that there are other considerations especially on a cruising boat but normally you would want the engine as close to the centre of the boat as possible to optimise comfort and speed at sea!

we had one on our cal 40, its a engine placement thing

 

  • Like 1
Link to post
Share on other sites

I learned to "big boat" sail on a Hunter 33 with a saildrive, and thought, when I bought a larger, more traditional sailboat with an inline drive, that I'd miss it.  Completely wrong: not only is the maintenance easier, but the propwalk makes docking our very momentum-carrying hull a comparative breeze.  I don't even know how much more room I'd need to get on the dock without my stern being sucked in by the prop.

Link to post
Share on other sites

Not sure azipods on sailboats are the right direction haha but who knows, would save money on the thruster.  From a little googling it looks like 50hp is about the reasonable cuttoff for monos and you can double that up for cats.  Beta seems to be doing things right.  I like the options they offer. The Kubota is bullet proof and I like that they have stepped up there marine package.  Much cleaner cooler and after cooler package and better arrangements of pumps, turbo and alternators.  Seems like a good company.  We are very happy so far with ours. 3k plus hrs and that's all I'll say before murfy hears. Would be a hard one to say what's better, I think in a new build like DDW I may lean to saildrive if I could spec out the whole thing. In a fin keel mono or cat I don't think there is any comparison.  The prop walk thing for Chris is a little deceptive, you end up learning to drive a boat based on what it has.  We had a big fixed prop and went to four blade max, way different handling bit would never go back. Almost two completely different boats and you learn to drive both.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...