Is There an Alternative to the Yanmar SD50 ?

[tpoffen]

Has anyone replaced their SD40 or SD50 with the ZF SD-10? If so, are you happy with the results? We are currently hauled out on the hard in St. Maarten and discovered that our starboard SD40 was completely full of water instead of oil (just bought the boat, 10 years old, surveyor only noted small amount of water mixed in with the oil). We'll get a SD50 installed if there's no better option...

Thanks,
s/v Compass Rose
2001 FP Bahia 46

[motion30]

Interesting Mercuriser switched from the dog style to cone clutch when they introduced there bravo series drives This was considered a more heavy duty style drive They are good for over 525hp although many people have used them with 1000hp motors Higher power requires regular marine transmissions Being in the marine service bussiness I remember the wrong type of drive oil would render the clutch totally useless Merc developed a semi synthetic oil for these drives Sail drive or sterndrive they simply are not as reliable as an inboard

[cbax]

A good alternative to ZF and Yanmar saildrives: Twin Disc model SeaProp60 (also available in the hybrid version with a 5 kW motor and generator).
Already seen on NANNI, Sole, Beta engines

[claire]

We did the same switch from SD40 to SD50 on one of our engines for the same reason: SD40 was full of water. Actually, the SD40 had filled with water a first time, when one of the bolts holding the lower part of the saildrive had not been tightened. It filled up a second time, after the mechanic who "fixed" the first problem, overtightened and broke the bolt without telling us.
Over time, owning a Yanmar saildrive forces you to become a mechanic, or at least knowledgeable enough that you can direct a mechanic in every detail of the needed maintenance.
We have now "lapped the cone" on our SD40 and SD50: once each, preventively, after 600 to 800 hours. They would probably have lasted a good few 100's of hours more, as we handle the throttle with great care, but we had a golden opportunity to have it done recently in Tunisia, with a great mechanic who knew the procedure and charged very reasonnably. They also seem to do the procedure routinely in Marmaris, Turkey, for a decent price.

If you go for the SD50 (I am afraid, other than changing the engine, you probably won't have much choice), make sure to have the documentation with you, that describes the cone lapping procedure: it will come in handy at some time.

[claire]

Yanmar instructions for SD40/50 cone lapping.
These pics have been useful to us.
Once you have the clutch assembly out, be aware that the first big nut you want to unscrew is a left hand screw nut that is caulked: carefully lift the caulking before unscrewing: undoing this nut has always been the most difficult and time consuming part of the operation for us and has required a special strong #27 key or other tool.
If you need the service manual, email me.