Saildrives vs Inboard

[Open-d]

Originally Posted by Mystic38

Well, you have made your mind up so its not clear why this thread,..?

But, anyway, you have presented your opinion as fact, so let me refute the "they concentrate weight to the rear instead of centered" statement.

The weight is where the designer puts the engines.... put them aft, the weight is aft, put them fwd and the weight is fwd.

So, in a condomaran design where the engines are under bunks or in the transom then yes the weight is aft.. however..do you not think that this is factored into the design of the vessel? Boat design is simply an exercise in tradeoffs, and such a configuration gives significant extra internal usable volume..

I own a St Francis 44, where the engines are midships as are the saildrives.. so the weight is actually more balanced than if there were shafts... but again, this has nothing to do with sail drives and all to do with vessel design.. the tradeoffs in this case are reduced usable internal volume to the benefit of narrower hulls, sleek exit and a better sailing design.. in this case, sail drives allowed Lavranos to develop this sleek fast hull... (at the expense of wide hulls and lots of interior volume..a tradeoff i fully accept)..

you or anyone is welcome to not like sail drives, but the reality is that they are nothing more than a tool for the designer to muck about with various layouts and design options.

Too snarky to read.

[johnn33]

It is possible to get a hydraulic powerpack giving constant rpm at best engine efficiency, but some losses caused in the hydraulics. You gain in quietness, space, optimum weight distribution, and a choice of shaft or saildrive leg.
John

[boatpoker]

Originally Posted by johnn33

It is possible to get a hydraulic powerpack giving constant rpm at best engine efficiency, but some losses caused in the hydraulics. You gain in quietness, space, optimum weight distribution, and a choice of shaft or saildrive leg.
John

Standard equipment on the old Fisher catamarans.... one Pathfinder diesel, two hydraulic drives.

[MJH]

Originally Posted by Chotu

There IS an alternative. The V drive.

V-Drive is as bad or worse than a sail drive, it just adds one more part to maintain and/or eventually replace.

Both saildrives and v-drives are design driven to either make a specific interior plan work or to save manufacturing costs...they have little to do with simplicity, long term reliability, and reduced ownership expenses.

All boats are tradeoffs but I wouldn't consider a boat with either of these features.

~ ~ _/) ~ ~ MJH

[ThereAndBack]

I just replaced two saildrives. However, I replaced to engines at the same time. The mechanical gear was just worn out... But, that is gear that was over 20 years old and had many thousands of hours on it. It had been neglected and not maintained to spec. It still worked when I replaced it all.

So people that are considering all the chatter in this thread, here is a real world opinion. I like my sail drives. They lasted 20 years before replacement. They are rather simple to service when we haul for a bottom job. They allow my props to sit in front of my rudders without compromising my use of space. The engine rooms I have allow me to get all the way around the engine and sail drives meaning it is easier and more likely I'll do service and keep them in good order. They're DEAD SIMPLE to replace if you ever have to do it, no alignment issues. They remove the need for the raw water seacock for engine cooling through the hull (built into the SD). They remove alignment issues. They remove the stuffing box and shaft tube from the equation.

I've had a monohull with a typical gearbox and shaft. I liked it too.

Like everyone is saying, everything is a trade off. But I for one, would not hesitate to buy another saildrive boat so long as it is well designed and installed. No matter what, there are going to be things to worry about. In terms of overall boat satisfaction, I doubt the saildrive vs shaft driven is going to be something you think about often and you'll probably have pretty similar expenses and maintenance between the two if you're someone that maintains a boat properly.

[boatpoker]

Originally Posted by MJH

V-Drive is as bad or worse than a sail drive, it just adds one more part to maintain and/or eventually replace.

Both saildrives and v-drives are design driven to either make a specific interior plan work or to save manufacturing costs...they have little to do with simplicity, long term reliability, and reduced ownership expenses.

All boats are tradeoffs but I wouldn't consider a boat with either of these features.

~ ~ _/) ~ ~ MJH

I've seen V-drives where the only way to adjust the stuffing box was to jack up the engine.

[Bunnellr]

I have volvo saildrive and rope cutter. 10 yes old and all working well.

[aljunina]

Just get a sail drive. I have crashed mine on coral reefs twice no problem. Motored tens of thousands of miles, once in 20 years from stupidity caught a fishing line in it and tore out the shaft seal but now closed all the gaps so that can't happen. You get better efficiency with a sail drive as your prop is facing "true" aft. They probably only last 30 or 40 years they are basically the end bit of an outboard.

[Gavin French]

Well, here's my experience. And I now think i have the best of both worlds, but was not easy. I have a year 2000, custom built Loch Crowther 48 from a yard in Australia. It is essentially a customized Catana 475. The build was fantastic and i remain in awe of the boat. But the drive train was its achilles heal from the beginning. Yanmar engines (amazing) Yanmar saildrives SD 50 (crap). As did the original owner, after purchase i had all the usual saildrives issues. The legs had been replaced once already when i bought the boat. Leaking oil seal requiring separating engine and saildrive repeatedly, slipping clutches repeatedly, galvanic corrosion... I eventually got to the point where i could lap the clutch coves myself in about 80 minutes. I hated them.

In 2018 I bit the bullet and replaced them with beta engines (kubota blocks), and oversized hydraulic v drive transmissions. Beta 50 with ZF 63IV transmissions built by Hurth. Big engineering and fiberglass job to change from a saildrive hole to shafts and strewn tubes. Thus I have now all the pros of stern engine rooms and the advantages of a robust regular transmission. Can offer more details if interested. The engines are reversed pointing forwards and the v drive reverses things with shafts exiting under the engine. Yes, the alignment was very difficult but made easier with R and D couplings. Shafts are just over a meter long. Flexofold props.

I looked extensively at new saildrives as it would have been cheaper and easier than the retrofit i did. All sources say the SD50 was one of the worst etc. But Beta offers just 200 hours warranty on their saildrives. That speaks for itself. Others much the same when i dug deep and asked lots of questions.

I also looked extensively at electric propulsion. But add full-time luge aboard cruisers our usage pattern would require a dc generator and the cost was triple that office two new diesels.

I think its an issue of usage pattern like everything. If you use the motors to get out of the marina and back in, with 100 or less hours a year on the engines, then saildrives are ok. Even then, but certainly for real usage and distance cruising, shafts are the only way to go. Saildrives are for boat builders, shafts are for boat owners.

[Gavin French]

Tidbits I forgot the first time.

My engines are now much quieter then the higher rpm 39hp Yanmar and saildrives.
The stuffing box or PSS Shaft seal is adjustable without moving the engine. Some yoga position required yes.
It's true, no one wanted to do the install, and i ended up doing it myself.

When you talk to transmission experts and manufacturers at length, it all comes back to usage. Hurth talks in categories: pleasure, light... all the way up to commercial which is essentially continuous usage. The categories are defined by hours of use per year. And the transmission they suggest hinges on your usage pattern.

A mechanical, cheaper, v drive could have fit my engines, but not my usage pattern.

So its really about hours of usage.

[Tin Tin]

Originally Posted by Gavin French

Tidbits I forgot the first time.

My engines are now much quieter then the higher rpm 39hp Yanmar and saildrives.
The stuffing box or PSS Shaft seal is adjustable without moving the engine. Some yoga position required yes.
It's true, no one wanted to do the install, and i ended up doing it myself.

When you talk to transmission experts and manufacturers at length, it all comes back to usage. Hurth talks in categories: pleasure, light... all the way up to commercial which is essentially continuous usage. The categories are defined by hours of use per year. And the transmission they suggest hinges on your usage pattern.

A mechanical, cheaper, v drive could have fit my engines, but not my usage pattern.

So its really about hours of usage.

So what is your usage pattern? How many hours on the engines since install?

[RaymondR]

Originally Posted by boatpoker

Standard equipment on the old Fisher catamarans.... one Pathfinder diesel, two hydraulic drives.

Modern hydraulics with axial piston, variable displacement pumps and gerotor motors offer very quiet, compact, reversible power transmission systems.

Using either a thru drive to the second pump or mounting one each end of the single engine to drive two bolt on pods would provide a system with unequaled options for engine placement and since every moving part runs immersed in oil under a head of pressure they tend to be mechanically reliable.

[smj]

Originally Posted by boatpoker

Standard equipment on the old Fisher catamarans.... one Pathfinder diesel, two hydraulic drives.

That was standard equipment on the older Catfisher 28. The newer Catfisher 32 came with a single diesel coupled to a Sillete outdrive.

[Gavin French]

Originally Posted by Dsanduril

I own two of them, not sure I’d recommend them over a saildrive or a straight shaft. They serve their purpose, and I’m not going to throw them away, but...

The stuffing box/shaft seal is under the engine and a royal pain to access, and yet with a shaft drive this is the one piece that is nice to be able access. And if the shaft seal drips the shaft flings saltwater all over the bottom of the engine, rusting out the oil pan.

You can’t install any of the flexible disc couplings because the shaft would put them in tension, and they are all made for compression. Which means you have to be dead on with alignment. But you don’t have easy access to the stern tube to do your sights or check your center.

Those are the things I’ve learned from living with two of them for four years.

Accessing the seal is difficult, but I dont find it bad compared with many boat tasks where access is the issue.

I have a small metal cover that sits over the seal to prevent water soaking the base pan if any did leak in , trick from a fisherman friend who had replaced his base pan.

R and D marine do indeed make flexible couplings specifically for v drive transmissions and i have two installed.
You still need to be right on with the alignment, but their couplings can be used to align the engine with everything all bolted together using their red bolt system. Really works.

My usage pattern is around 500 hours per engine per year. Hurth puts that above pleasure category and above their recommendation for their mechanical v drive.

Shaft angle looks like any other you might see and engineer analysis shows no significant difference from 90 degrees of a saildrive. And i was able to mount the engines level.

I am no expert, but i spent a couple of months doing nothing else, and about a year in research and prep, and now two years of running them.

[Gavin French]

39 hp 3 cylinder Yanmar, sd 50 saildrive, worn folding props became 50 hp beta, hurth zf 63iv trans, new flexofold props 18x13.

One engine 6 knots, two engines 7.5 knots became one engine 7.5 knots and two engines 9 knots.

And now able to motor into twenty knots head wind with one engine at 5.5 to 6 knots where previously that required running both.