Sail Drives..Like em?

[robert sailor]

Years ago we had choices when purchasing a new boat. If you wanted to save money you could have a sail drive installed rather than a shaft drive system. When you went to sell it you always took a bit of a beating if your boat had a sail drive, but these days almost all the new boats have sail drives. I know that sail drives don't need to be alined and I know they present a nice underwater profile to reduce drag, but they had these benefits in years past and were considered by most buyers as a cheaper alternative to a better system.

Is this just a way to lower costs or are there other reasons for not installing shaft drives??

[impi]

Originally Posted by robert sailor

Years ago we had choices when purchasing a new boat. If you wanted to save money you could have a sail drive installed rather than a shaft drive system. When you went to sell it you always took a bit of a beating if your boat had a sail drive, but these days almost all the new boats have sail drives. I know that sail drives don't need to be alined and I know they present a nice underwater profile to reduce drag, but they had these benefits in years past and were considered by most buyers as a cheaper alternative to a better system.

Is this just a way to lower costs or are there other reasons for not installing shaft drives??

Must say I dislike the Yanmar SD 50's with a passion! Not sure I would want to have a shaft though!

[colemj]

The saildrive was introduced in 1973 and has gone through some improvement since. Some of the popularity now could be from the SD having been around long enough, and through enough iterations, to have proved itself. Manufacturing cost is certainly one reason for their current popularity - they are and always will be cheaper to install than a shaft drive - but another reason is boat design. The newer designs are not only more amenable to SD installations, many are actually such that it is difficult to install a shaft drive. Catamarans are one example and shallow hull light displacement boats are another. The compromises in these boats with engine placement, prop shaft angles, shaft support engineering, etc for installing a shaft drive are too large for the design/market. I don't know whether that is a chicken/egg problem.

I don't know of any boat past or future that provided a drive system option on purchase. They may have (or do) exist, but it seems unlikely that a builder would have both options since there are different design/engineering considerations that would be costly to leave open. Custom or semi-custom non-production boats would be the only ones that would have the possibility.

Mark

[Dulcesuenos]

We weighed both options looking for our current cat and the next one we close on soon and really prefer shaft drive to sail drive. I know saildrives are the way of the future, but even though shafts may not be perfect and require more tweaking occasionaly, the amount of work to keep em going seems less, and shft drives seem more robust for long term, cruising.
A little birdie told me that Yanmar is no longer going to be making the smaller saildrives and that parts are going to be even more pricey and scarce in the future.

[robert sailor]

In the past you could buy a Wauquiez Pretorien 35 in either a sail drive or shaft. You could buy a Niagara 35 in either a sail drive or shaft. I am very familiar with these boats and they are at the top of the list for good older boats to take offshore in this size range and you had a choice when you bought them but the shaft was quite a bit more yesterday and today.

[Oceanride007]

I like the simplicity of a straight shaft less losses in bevel drives.
Not sure but I think thrust pads in gearbox are nearly always white metal pads which are more reliable than the thrust rollers that I think saildrives have.
Saildrives may suffer from galvanic action.
Sail drives probably need to put on the hard to change the oil. (can anyone confirm)
Saildrives are vulnerable to SW contamination, oil seals and wear would be a worry.
However sail drive puts the propeller in the more parallel part of the water flow. Which has several advantages such as more quiet and less seal/bearing wear.
Amels have them sort of, Henry Amel was no dope, his boats are designed to last.

[Capt RonB]

Saildrives like their powerboat brethren, the stern drive, add complications and therefore maintenance issues. The Volvo and Yanmar drives that I've worked on seem reliable enough but I think simpler is better so for me straight shaft drive makes more sense even if it costs more.

In my experience, fluids in the lower unit can be changed without a haul out via a small pump or other suction device.

Saildrive maintenance issues include protecting under water metal alloys, keeping barnacles off all that underwater surface area, shaft seals and seal leaks, and the large hole in the bottom of the boat usually protected by rubber gasket. I have heard of a horror story where a line wrapped on a prop ripped half the drive leg out of a catamaran and flooded a hull. I tend to think that if a wrapped prop shaft in a straight drive was pulled out, that a bilge pump might keep up with the inflow?

Just my opinion.

[jeremiason]

Saildrives, like I/O drives require more maintenance than a traditional prop shaft/transmission.

They are a cool idea and allow much more interior space, especially on Catamarans, but they require maintenance, which some owners don't realize until they are replacing their original unit.

The real question to ask is how many people have had to replace saildrives as a result of corrosion or damage?

From my own knowledge and experience, I would guess a lot more saildrives are biting the dust than traditional transmission/prop shafts.

[impi]

Originally Posted by jeremiason

Saildrives, like I/O drives require more maintenance than a traditional prop shaft/transmission.

They are a cool idea and allow much more interior space, especially on Catamarans, but they require maintenance, which some owners don't realize until they are replacing their original unit.

The real question to ask is how many people have had to replace saildrives as a result of corrosion or damage?

From my own knowledge and experience, I would guess a lot more saildrives are biting the dust than traditional transmission/prop shafts.

Yes ... spot on! Found the life on cone clutches has a direct bearing on complete oil change which is done with the boat in or out of the water. We change oil every 120 hours because we have found that despite this being low hours it really saves in not only money, but also time to change cones.

Still ... I can't help but feel the SD 50 is OLD TECHNOLOGY ... my goodness ... what were he engineers thinking!

Speak to the charter guys in the BVI's and other places, and they will tell you they keep boxes of cones as regular replacement parts.

We are considering the SD 60 as an upgrade, but will have to keep an eye on that ones performance first.

[colemj]

Your cone clutch problem is a wide-spread Yanmar issue - not a general saildrive issue. The Volvo saildrive does not suffer the same general problem. The top end of the Volvo saildrive is the exact same as their shaft drive transmission - cone clutch included. The only difference is the length of the drive shaft on the saildrive.

Saildrives and I/O's are completely different beasts, although they may look similar on the surface. To put them in the same category is strange or unenlightened.

I have owned both saildrive and shaft drives and do not find the saildrive any more maintenance. Both need their oil and zincs changed routinely, and both need periodic changing of their seals/stuffing. Both also need to be concerned about electrolytic corrosion from hot wiring or bonding/grounding issues. Galvanic corrosion is extremely rare with both.

The saildrive requires a bit of extra antifouling paint (non-copper). Also, electrolytic corrosion will cost more to repair than a shaft drive.

As for damage, this forum is full of questions from people who have damaged struts, shafts, stuffing boxes, cutless bearings and couplings on their shaft drives.

So beyond the antifouling, I do not understand all the "extra maintenance" the saildrive requires that I am not doing. Perhaps you shaft people can explain it to me before I sink my boat?

Ironically, having owned one Hurth shaft drive and two Volvo saildrives, the only failure I have had was the Hurth. I don't draw any conclusions from that.

Mark

[impi]

Originally Posted by colemj

Your cone clutch problem is a wide-spread Yanmar issue - not a general saildrive issue. The Volvo saildrive does not suffer the same general problem. The top end of the Volvo saildrive is the exact same as their shaft drive transmission - cone clutch included. The only difference is the length of the drive shaft on the saildrive.

Saildrives and I/O's are completely different beasts, although they may look similar on the surface. To put them in the same category is strange or unenlightened.

I have owned both saildrive and shaft drives and do not find the saildrive any more maintenance. Both need their oil and zincs changed routinely, and both need periodic changing of their seals/stuffing. Both also need to be concerned about electrolytic corrosion from hot wiring or bonding/grounding issues. Galvanic corrosion is extremely rare with both.

The saildrive requires a bit of extra antifouling paint (non-copper). Also, electrolytic corrosion will cost more to repair than a shaft drive.

As for damage, this forum is full of questions from people who have damaged struts, shafts, stuffing boxes, cutless bearings and couplings on their shaft drives.

So beyond the antifouling, I do not understand all the "extra maintenance" the saildrive requires that I am not doing. Perhaps you shaft people can explain it to me before I sink my boat?

Ironically, having owned one Hurth shaft drive and two Volvo saildrives, the only failure I have had was the Hurth. I don't draw any conclusions from that.

Mark

Agreed … volvo has a better mechanism than does Yanmar although I personally prefer the Yanmar engines.

[tamicatana]

FWIW, Volvo invented the saildrive

I'm surprised to hear that saildrives are cheaper given their complexity. I find that saildrives require more attention to maintenance but so far I've been ok with mine.

[colemj]

They are cheaper for the manufacturer to install, not for us consumers to purchase.

Mark

[tamicatana]

Originally Posted by colemj

They are cheaper for the manufacturer to install

I was thinking of the beefy layup and particular design my cat has in the area where the saildrive transits the hull, actually, but I suppose that's easier than planning the overall hull layout for the further-forward engine that would have been necessary with a shaft. I'll have to look closer at my friend's shaft-drive Leopard 38 sometime. Interesting.

just remembered: if I recall, the afore-mentioned friend wrapped a crab trap float and the shaft-driven system had a surprising amount of damage to the tranny - have to ask him for the deets

[colemj]

That layup and mount system comes with the saildrive. All the manufacturer needs to do is cut a hole in the hull and glass on the supplied mount system and bolt on the engine/saildrive. Very easy and inexpensive for them compared to having to make engine mount rails and pans, struts, logs, stuffing boxes and align the whole shebang.

They most likely get the units much cheaper than us consumers also.

You are wrong about your friend. Shaft drives and trannys never have any problems at all, or any weak points. Saildrives, on the other hand, violently fizz away and throw sprockets everywhere at the slightest touch of moisture. Not to mention the thousands of boats that sink yearly due to that giant hole in the hull.

You haven't been reading the expert threads on this subject, have you?

Mark