Sail Drives VS direct drives

[LLizzard]

It's surprising to me how many cats have sail drives. Never understood power boats in salt water slips with stern drives, let alone cats with aluminum sail drives. However eliminating sail drives eliminates a lot of potential boats for me to consider.
I can come up with cons for sail drives:
Aluminum in salt water
Hot marinas/ stray current
Perfect zinc matching/ maintenance required
Drive oil changes, do you have to haul for that?
More frequent haul outs required vs direct drive

Are there any pros for sail drives?

[sy_gilana]

The only pro I know of is that the engine can be mounted further aft, thereby giving more living space.

Shafts are better, but only work on bigger cats.

Worst design I have seen is where the saildrive is AFT of the rudder, can you believe it?

Oil change can be sucked out and refilled from the top, but not the best way.

[Training Wheels]

More efficient. Less vibration.

[robert sailor]

Less expensive to build with sail drives

[LLizzard]

I can see the better efficiency, as there is no down angle on the shaft, hence all the propulsion is forward, not forward and up.
Would not have a problem with them if they were made of bronze, like the pod drives now being put on power boats. I just don't like a multi thousand $ aluminum drive in salt water.

[clockwork orange]

Ive seen plenty of sail drives that don't seem to have any corrosion issues, maybe more of a perceived problem, maybe not. Maybe they could be made out of composites. I love bronze as a marine material but too heavy for me.

Steve.

[sy_gilana]

The down angle vs horizontal thrust benefit (which is debatable) is paid for by transferring through two 90 degree helical gears.

Very important to maintain engine mountings, as if they break it could sink the boat.

[Palarran]

I think a lot of the new cats have sail drives aft of the rudders and agree, that's not very good. But saildrives do allow a huge amount of added space to the cabin areas. I have a shaft drive but would certainly consider a saildrive cat for ownership. The problem with shaft drive is also the distance from the prop to the rudder. I have about 6" with prevented me using folding propellers. Instead I have feathering, which are good, but not as low profile as the folding. Also, the prop wash is pretty heavy on the rudders which can help in docking but is less efficient when motoring distances. I probably wouldn't let this feature decide a purchase.

[ZULU40]

Originally Posted by LLizzard

It's surprising to me how many cats have sail drives. Never understood power boats in salt water slips with stern drives, let alone cats with aluminum sail drives. However eliminating sail drives eliminates a lot of potential boats for me to consider.
I can come up with cons for sail drives:
Aluminum in salt water
Hot marinas/ stray current
Perfect zinc matching/ maintenance required
Drive oil changes, do you have to haul for that?
More frequent haul outs required vs direct drive

Are there any pros for sail drives?

compared to direct drives that run at an inclined angle theyre more efficient, expect around 10% more power delivery
and they come with trims, possible anti cav plates etc
you can turn the boat on directional thrusts

add to cons, theyre not well matched for cat power requirements, more usually for much more powerful engines
therefore cost more to buy than they might

[roland stockham]

You missed what is for me the clincher. With a sail drive the integrity of the hull relies on a large rubber seal around the leg. to make it worse it is a long leg. Even a small impact at the prop risks breaking that seal and no pump system will stand a chance if it fails. On a mono where it is behind the keel it has some protection but on a cat there is probably nothing.

[JOHNMARDALL]

The sail drive saves space, does not require engine-gearbox/shaft alignment and uses the same tried and true gear train concept as an outboard motor, with little or no propwalk in reverse. The solstice must be properly maintained, especially with regard to anodes.
This is not new technology and was introduced by Volvo Pentax about forty years ago. Most or all of the marine gearbox makers offer a sail drive with a multi-hull year warranty.
Not a reason to pass on the boat of your dreams but get a survey from an approved service shop.
Good luck
John Mardall
Vetus Maxwell Group

[Steadman Uhlich]

To JOHNMARDALL's point about the need for anodes:

A picture tells a story:

[grjfield]

Originally Posted by Steady Hand

To JOHNMARDALL's point about the need for anodes:

A picture tells a story:

The good news is...looks like the saildrive became the anode for the prop!

LOL

...looks like a Gori folding prop...still in great shape!

When I bought my sailboat, the zinc had not been maintained and the saildrive had just started to degrade. Although I knew it would eventually need replacing, copious amounts of grinding, followed by lots of JB weld extended its life by 5 years before installing a new electric saildrive from Sillette.

fyi...the saildrive is bolted and glassed in so no rubber boot to leak.

[sailon46]

Originally Posted by Steady Hand

To JOHNMARDALL's point about the need for anodes:

A picture tells a story:

I am in preliminary plans in sailing my bene 52 from st Croix us I to Azores or Gibraltar if time permits in mid April :2017. Let me know if interested
Ernie on the Mary Jane

[jmschmidt]

Well that settles it, the jury is in and sail drives are out. Couldn't agree more. Should be outlawed for safety reasons. Aside from what nearly everyone else had said here if you hit something substantial with your sail drive and you're probably going to sink your boat. Nobody sailing far from shore and safety should have one. Should be reserved for racing boats, preferably racing boats that can be removed from the water regularly and cheaply. The big charter companies love them because they get ride of their boats at least every five years before real maintenance problems crop up. They may rethink their strategy when their owner's take delivery and realize the resale value has collapsed.