inboard vs. sail drive diesels

[William C. Wins]

Fora full keel wooden boat what are the pros and cons of an inboard deisel vs. a sail drive? It seems to me the sail drive sort of hangs there unprotected whereas an inboard with a shaft hole has the deadrise to protect the prop.

[Mychael]

I have been told by a Yanmar dealer that maintanence costs and frequency are higher with a saildrive.

Mychael

[wet feet]

If you try to install a saildrive in an existing full keel wooden boat,you may have some major modifications to do in order to create a large enough hole for the saildrive leg to fit through.A conventional stern tube tends to be much smaller.

[William C. Wins]

The boat has not been designed yet. Traditional would be full keel withdeadrise cutout for prop and rudder behind counter stern. The other version for sail drived would have less of a full keel with at least three feet between trailing edge of keel and hole for sail drive Barn door rudder would be after that.

[hiracer]

I've owned a boat with sail drive and found that most of the critics of this system are wrong. It is more efficient, quieter, and offers much less vibrations to the boat. Corrosion was non-existant, but this was on a boat without A/C power which I think was significant.

Sail drives necessitates a truly huge hole in the bottom of the boat, which theoritically is a big liability. If you look at actually statistics, however, I suspect that prop shafts exiting the boat and problems with stuffing boxes and the like pose a bigger actual liability. But I don't have any real hard data to back up that suspicion.

Saildrives in the long run will require higher maintenance costs because every 5 to 7 years the rubber membrane around the thing is supposed to be replaced, but I'm unaware of anybody who actually replaces these things on schedule.

My current boat has the traditional prop shaft. After long periods of motoring, I certainly miss the saildrive.

Buyers in the U.S. are generally biased against sail drives.

[Buc]

I've had a Yanmar saildrive (SD20) for eight years and the only disadvantages I've noted are the inability to lock the prop in the horizontal position so the blades will stay folded under sail at slow speeds, and the prop must be removed to replace the zinc.

On the plus side, I like the smooth running and the absence of water in the bilge from the obligatory drips a stuffing box requires.

As noted, the rubber membrane will require replacing someday, neither cheap nor easy -- we did it a few years back as insurance required it -- but the Yanmar drive has two membranes and ample warning if it's failing before it becomes critical. Last I looked, Volvo drives used a single membrane.

If you're planning on cruising to faraway places, the shaft/strut probably has the advantage of being more easily serviced wherever you may be, though most parts of the world outside the US and UK are metric, creating compatibility problems from one system to the other.