Saildrives vs Inboard

[contrail]

Originally Posted by Chotu

There IS an alternative. The V drive.

These can be very hard to service, including shaft seal/packing gland, etc.

[rallyman1122]

Originally Posted by warren2

I have volvo saildrive and you cant attach a rope cutter - big problem

Not so. Starry Horizons has installed ripe strippers on their Volvo sail drives on their Helia 44. You can find information on their blog.

[sailr69]

Originally Posted by Tin Tin

Why would a sail drive be less expensive than a simple shaft drive? Did a manufacturer tell you this?

maybe cheaper because less labor to install, also outboards have saildrives right. usually used units for saildrives. like everything else, use proper electrical installations. generally last longer then the engines. in terms of hours.

[edlepera]

Originally Posted by Tin Tin

So as we are in the multihull section of the forum, we are usually talking two engines. When we first looked at buying a cat in 2001 80% of them had the engine "indoors" ie. accessible under a bunk or cupboard. Those boats all smelled of old diesel/oil etc, were difficult to service etc. We ended up with outboards as my wife felt ill with that smell. Since then many cats had engines installed in the rear of the hulls behind a sealed wall. We bought one on those in our second cat and loved it. Easy to work on engines (and sail drives) , separate engine compartment, easy to keep clean and dry and free of muck. Also less noise and vibration.


Now of course this loads weight into the sterns, so they design the hulls with that in mind of course. If you are a sailing perfectionist and want the weight centered and use shaft drives then go for it, if you can find a modern cat like that now days.


Sail drives are surprisingly robust, usually hung behind protecting keel or skeg. The positives and negatives include but not limited to:


Positives:
1 Engine/SD can be lifted straight out, no manhandling through the saloon

2 Easy to service and keep clean
3 No internal odours
4 More efficient prop drive angle

5 No bent shaft, alignment, balancing, cutless bearing, dripping seal issues




Negatives:
1 Need more anti corrosion care underwater
2 Clutch wear in older modelsoy
3 Oil seal maintenance complicated - but may be so on shaft gear box too
4 Weight concentration at rear (although some old model cats have sail drives further forward in the middle of the hull sloped to one side - looks like a headache to work on)
5 Potential for catastrophic damage from mooring line wraps around prop where SD becomes unseated and breaks seal


......there maybe more

what about electric saildrives

[Tin Tin]

Originally Posted by edlepera

what about electric saildrives

Never seen one. I like the concept - practicality may be an issue.



I hear that Lagoon experimented with electric drives and made them an option (that did not work out well) , soon most people replaced the problematic electric drive with standard diesel. I have no idea of actual numbers though, just hearsay.



There is lots of debate on this forum about it though especially as new technology becomes more affordable.

[bodgy]

One major problem for me is now Im looking at a Bavaria 34 to purchase. All looks very good, but she has a clapped out, under powered green death/anchor with a sail drive.

In a shaft drive boat I would replace with a Beta, they will provide engine mounts to fit the old green death bearers.

With the saildrive, replace the lot or give the spawn of Satan $$ for a new donk.

[Tin Tin]

I thought I read somewhere Beta had adapters to fit Volvo SD, but no personal experience of that.

[johnn33]

Here is a rope cutter for a saildrive, and there are others
https://ab-marine.com/product/shaft-...ildrive-model/
John

[danstanford]

Originally Posted by Tin Tin

Never seen one. I like the concept - practicality may be an issue.



I hear that Lagoon experimented with electric drives and made them an option (that did not work out well) , soon most people replaced the problematic electric drive with standard diesel. I have no idea of actual numbers though, just hearsay.



There is lots of debate on this forum about it though especially as new technology becomes more affordable.

I have an Oceanvolt electric motor with a saildrive and it works perfectly. Range is the only issue and I have dealt with that by buying a generator to put on deck if I need it to augment range in some situation.

[GordMay]

Originally Posted by Tin Tin

I thought I read somewhere Beta had adapters to fit Volvo SD, but no personal experience of that.

Indeed, they do.
Beta Marine Saildrive Solutions
Saildrive Solution 1: Replacement Engine and Saildrive Leg
With this option we supply a complete replacement saildrive unit, that just ‘drops into your existing GRP moulding’.
Saildrive Solution 2: Replacement Engine with Adaptor for Existing Saildrive Leg
Although we would always recommend replacing both engine and saildrive together, should your existing saildrive be known to be in excellent condition or has been recently fully overhauled this option facilitates a reduced replacement engine cost.
More ➥ https://betamarine.co.uk/saildrive-solutions/

[bob and sharon]

I'm on my lunch break right now, we're most of the way through a saildrive replacement today. I work at a boatyard as a Lead Tech/diesel mechanic, a great job!
Saildrives are what they are, they are not inherently bad, they simply have to be understood.
First - if you're buying a boat with saildrive(s) have an oil analysis performed to make sure there is no water contamination, yes there will likely be some fresh water (from condensation), but there should be zero sodium/water. The analysis will also tell you the condition of the bearings, gears, etc...
Secondly - saildrives are prone galvanic corrosion. Think about it; you have a large piece of aluminum submerged in seawater, along with stainless steel and bronze. The voltage potential of aluminum is very close to the voltage potential of zinc (which is what your protective anodes are made of). So if the saildrive anodes are depleted over time, or due to stray current corrosion (a wiring issue), the saildrive leg will instantly begin corroding. You see photos online all of the time showing decimated saildrive legs! So be sure that your saildrive anode is changed on a regular basis, and that the boats bonding system is operating properly. Yes I know that Volvo tries to isolate their saildrives, but it rarely happens.
Third - saildrives are more maintenance sensitive, and are unique in this sense. You must change the oil and anodes, inspect or replace the bellows seal as per the manual, it's the only thing between you and the briney-blue! The boat must be hauled-out to replace the bellows, Yanmar and VP recommend this be done every 2 years. So plan on hauling-out your boat more often if you have saildrives.
Fourth - saildrives are way more expensive than a traditional transmission and shaft assembly. A Hurth transmission for a 50hp engine will set you back about $1800, cost for an average length 1-1/4" shaft say $600. A saildrive will be between $4200 and $7800, depending on what color it is. Green is more expensive than gray
Having said all of that; my wife and I are deep in the planning stages of retirement and we plan on purchasing a used 40-45ft catamaran that will likely have saildrives. Am I hesitant to do so? Not if I want to own a catamaran! And I do!!!
So enjoy the boat and simply learn about this new thing you own called a saildrive.

Take care.
Bob

[DougR]

Originally Posted by bob and sharon

Third - saildrives are more maintenance sensitive, and are unique in this sense. You must change the oil and anodes, inspect or replace the bellows seal as per the manual, it's the only thing between you and the briney-blue! The boat must be hauled-out to replace the bellows, Yanmar and VP recommend this be done every 2 years.
Bob

Saildrives are maintenance sensitive, yes, but certainly not unique in this sense.

Transmission oil has to be changed in inboard transmissions as well, same for the anodes found in transmission oil coolers. Yes, the vessel needs to be hauled to change the diaphragm, but not every 2 years as you state. The recommended change interval for diaphragms is every 7 years.

Saildrive installations don’t have to worry about repacking stuffing boxes like inboard installations do, and even more modern inboard stuffing boxes such as the “last drop” require bellows replacement on a periodic schedule.

Saildrive installations also don’t require periodic engine alignments and there is no cutless bearing to wear and cause problems....

So you have to make your choice and do your maintenance....lack of maintenance in either case will cause problems.

[Tin Tin]

The Yanmar SD 50 manual from 2009 says to inspect the diaphragms every year and to replace every 5 years, I recall someone saying Volvo was every 7 years.


The Yanmar has two diaphragms an A and B so a form of redundancy. If A fails water gets between A and B and sets off an alarm (Which is easily tested once a year).