Saildrives?

[DotDun]

Originally Posted by downunder

But it is interesting FP and Lagoon fit shaftdrives rather than legs to their trawler catamaran range. I wonder why?

Gee, it might have something to do with the fact that Yanmar and Volvo only fit saildrives on engines 75hp and smaller?

A properly maintained saildrive is no less reliable than a transmission/shaft. The majority of problems with saildrives are due to lack of maintenance.

Having a saildrive (actually 2) would never keep me from cruising the Pacific.

[Jim Cate]

Originally Posted by DotDun

Gee, it might have something to do with the fact that Yanmar and Volvo only fit saildrives on engines 75hp and smaller?

A properly maintained saildrive is no less reliable than a transmission/shaft. The majority of problems with saildrives are due to lack of maintenance.

Having a saildrive (actually 2) would never keep me from cruising the Pacific.

DD, I think that from your location in SW Florida, surrounded by marine facilities your outlook is reasonable.

But look at what you just said "A properly maintained saildrive...". Don't you see that proper maintenance requires rather frequent replacement of the seals, and that this is not so easy to do in the woop-woop.

As one who has actually spent years cruising in the Pacific, I can say that once away from the mainstream finding places to slip (haul out for you Yanks) isn't always possible. So, while you may say that having a saildrive wouldn't keep you from cruising the Pacific, I surely wouldn't advise the OP that there are no drawbacks to that selection.

And yes, there are certainly boats with saildrives successfully cruising. But, we personally know enough of them that have had serious problems to be disenchanted.

'Nuff said for now...

Cheers,

Jim

[ccgarnaal]

I would prefer a straight shaft and stuffing box.
(brass shaft and propeller so no zinc to replace and no corrosion to worry about)
Mine is 50 years old and everything still works fine.
I don't have a transmission / clutch that can freeze up but a manual controllable pitch propeller. The only thing to be afraid of there is parts, if i would ever do serious cruising i would probably take a spare propeller blade along.

Why stuffing box with grease lint are great. Because you can replace the grease lint seal in the water. Haven't seen that on a sail drive before.

As to propeller angle:
What i learned in Nautical college:
Downward is old fashioned and not done on any cargo ships unless hull form requires it.
Straight has been the way to go for better efficiency for a while.
Now the Marin institute in Delft is saying that the prop line should be parallel with the hull so that the water comes in at a straight angle. Thus some recent ships with azipods are build with slightly upward facing propellers to follow the hull curvature.

[amarinesurveyor]

I didn't intend to sound like I'm a fan of sail drives, I'd take a straight shaft over a sail drive if given the choice.
Brian

[colemj]

Jim, you are making a lot of noise about "seal replacement" and "efficiency losses" on saildrives without any actual personal experience or information about them.

The shaft seals on our saildrive are 6yrs old and working as new. The ones before these were 9 years old and looked like new when I replaced them only because I thought I should. Volvo recommends replacing these seals "if there is evidence of water leakage".

The only other seal that requires periodic replacement is the main hull seal. Volvo recommends replacing it every 7 years. Ours is 15 years old and looks like new. I have never heard of one of these seals failing outside a catastrophic hit to the saildrive itself. Almost every boat with a saildrive older than 7yrs has the original hull seal on it.

Surely, you "real" cruisers cruising in "real" places that are so far removed from any and all civilization can find a haulout facility every 7-9 years? Or maybe my simple Yank brain and soft SW caribbean body cannot fathom the distances and isolation of real cruising. Hell, I don't even know where "Whoop-Whoop" is...

Cone clutch reliability issues are isolated to certain Yanmar drives only and do not require any haulout facilities to rectify.

Efficiency losses through a saildrive is a red herring. The gears are helical and matched sets and any efficiency losses are engineered out through gear ratios and prop sizing. Exactly the same way it is done in a normal gearbox, except prop sizing can be more exact than many full keel and skeg boats with apertures and shaft drives. It isn't like these things are slipping and hardly turning while the engine screams at redline. I will bet that the practical mechanical efficiency loss (as measured by prop output as a function of engine torque) compared to a rather long shaft drive going through a stuffing box and cutlass bearing is immeasurable. Heck, I may even take the bet that the saildrive is more efficient.

I have owned boats with both saildrives and regular gearboxes. The only tranny that has given me problems was the Hurth gearbox, but both types have been equally reliable.

Mark

[DotDun]

Originally Posted by Jim Cate

But look at what you just said "A properly maintained saildrive...". Don't you see that proper maintenance requires rather frequent replacement of the seals, and that this is not so easy to do in the woop-woop.

Yes, when one makes the decision to own a saildrive, they are committing to proper maintenance. It's not an 'out of sight, out of mind' device.

But, properly maintaining a saildrive is no more onerous than any other system on your boat, in fact, it's quite easy. If one has the aptitude to change a prop, they can change the lower seals, it's literally a 30 minute job start to finish.

I change lower seals every haulout for bottom paint (30-36 months), the parts are <$20, it just makes sense. I change zincs every 6-8 months in the water. 2000 hours and 10 years with no issues. If I were long-range cruising I would carry spares, if a seal failed prematurely, I would change oil at short intervals until I could either haulout or find a nice beach where I could get 30 minutes of low tide.

If one drive fails catastrophically, I run on one engine (just like a monohull does - ) until I can get it fixed.

Oh yeah, I also protect all the underwater metal on my boat with an isolation transformer, again, when you decide to own a saildrive, you should consider any/all issues. Maybe your friend in Kettering, Tasmania should have thought about this?

IMO, for my boat, the pluses of a saildrive outweigh the minuses, hence I happily own and maintain two of them.

[geoleo]

There is also the factor that a saildrive can be pulled completely out and nearly sink your boat-which happened when a Lagoon 450 near Singapore was towing a dinghy. The helmsman backed up when he got to close to a tug/tow-forgetting about the dinghy behind-the dinghys towline got caught in the Yanmars saildrive ad yanked it hard sideways as the dinghy had drifted to be outside the opposite hull---the entire saildrive came up thru the hole flooding the entire hull as Lagoon had not properly sealed the engine compartments bulkheads-----these 450s are unlucky (or not navigated well).

[Cheechako]

Just say "NO" to saildrives.... or buy a Bayliner..... :>)

[Kettlewell]

The only thing I can say is that a bunch of cats with saildrives were having problems with them when I was down in the SW Caribbean. There were very few places to haulout a big cat and parts had to be FedExed in at great expense. I visited some boatyards and I noticed that without fail the cats were having work done on one or more saildrives. They seem to be more trouble prone than standard shaft set ups.

[hugosalt]

I usually don't post same info on 2 different forums, but subject came up on other forum few days ago so below is copy and paste.
Would add that one must keep up with zincs, easily done in water with 2 piece zincs around saildrive.

Happy New Year All!
Have Yanmar SD20 with folding prop on my 30" sloop, saildrive is 27 years old. No leaks, original seals...wanted to change seals
several times just because, yanmar dealer says not needed and
cited older units still going strong with original seals.
Am coastal sailor and would change seals if going offshore or if
did not know history of older unit.
Have gone bump in the night few times, one time sailing over a
substantial submerged tree with no problem. Saildrive sits somewhat protected behind keel, would rethink if more exposed
as could be on a catamaran.
Makes for very quiet motoring with no vibrations transfered to hull and bilge is dry as no shaft seal leakage and no critical shaft line up. My install my be somewhat unique as motor is turned 180 degree from normal install and presents easy access for inspection of saildrive seals and gear oil.
Almost forgot, there are actually two robust watertight seals
that have a sensor between them that sounds an alarm if
any water ingress. Alarm has never sounded other than when I
remove and test. There is a 3rd exterior seal/rubber flap not
water tight on the bottom of the hull/ saildrive leg that keeps
out growth.
One has to be careful about keeping raw water intake open and I have installed a 3 way valve to another thru hull if needed, i don't need to use but am very careful about keeping bottom/saildrive clean.
All in all am happy with yanmar sd20 saildrive, which are still made today...can not speak to Volvo drives...and certainly aware that many are not fans of saildrives.

Maybe some will speak to their personal experiences with their
particular makes and models.

Beware of experts with no first hand experience/knowledge in all things small and large.
Hope this helps,
Hugo

[44'cruisingcat]

Originally Posted by georgetheleo

There is also the factor that a saildrive can be pulled completely out and nearly sink your boat-which happened when a Lagoon 450 near Singapore was towing a dinghy. The helmsman backed up when he got to close to a tug/tow-forgetting about the dinghy behind-the dinghys towline got caught in the Yanmars saildrive ad yanked it hard sideways as the dinghy had drifted to be outside the opposite hull---the entire saildrive came up thru the hole flooding the entire hull as Lagoon had not properly sealed the engine compartments bulkheads-----these 450s are unlucky (or not navigated well).

That's what you get for towing your dinghy!

I've also heard of shaft drives falling out leaving a sizeable hole in the boat too though.

[smj]

Originally Posted by 44'cruisingcat

That's what you get for towing your dinghy!

I've also heard of shaft drives falling out leaving a sizeable hole in the boat too though.

I don't think I've heard of an outboard falling out leaving a size able hole in a boat. Maybe the outboard is a viable option to both shafts and saildrives. I know for me it is.

[amphibious1]

This is all very simple!!
The more moving parts you have..
The more time you spend maintaining or replacing those parts.

[DotDun]

Originally Posted by amphibious1

This is all very simple!!
The more moving parts you have..
The more time you spend maintaining or replacing those parts.

Please enlighten us as to the quantity of moving parts in a saildrive vs a conventional transmission...?

[sctpc]

This thread sounds like the Ferro cement, all the experts never had one but know from someone else there rubbish.

I have a Bukh saildrive came with the boat know nothing about it, in the maintenance Log, lower seals, prop anodes and five years ago the bladder was changed after the boat sat on the hard for 10 years under cover.
So I have no idea if thats considered high maintenance or not the boats 27.