Yanmar SD40/50 Saildrive poll

[Captain Bill]

Numerous threads and members have addressed the issue of slipping cone clutches on Yanmar SD40/50 saildrives. Some people seem to have the problem at less than 500 hours whereas my personal experience is that I have 12 years and 2500 hours on my drives without having any cone clutch issues. Member Panache5000 has come up with a very reasonable explanation of why the clutches slip in forward gear and are a maintenance nightmare for some. In a standard installation props are right handed and the forward gear is the bottom gear in the stack. These sail drives can however be set up for left hand props and in that case the forward gear is the top drive in the stack. If one comes to understand Panache5000's explanation the bottom gear has a spring which I assume is to help disengage the cone clutch against gravity (That may not be the actual purpose, only a logical supposition) and if the thrust washer is worn or not setup to proper clearances the spring will partially disengage the cone clutch by lifting the whole assembly which leads to slipping and glazing, thus requiring periodic lapping. I on the other hand have not had this issue, but my drives are set up for CCW rotation in forward, thus I use the upper gear which has no spring and thus does not suffer the problem. This is a bit of conjecture on my part but does seem to explain why I've had no cone clutch problems until recently. I should note that unlike most people who raise the issue my problem is that I'm getting some slipping in reverse on one drive, but because I am set up for CCW rotation this is the same gear most people seem to be having problems with in forward. So to see if there's any actual data to support my hypothesis I've decided to conduct a poll.

[cruiz9]

Hi Bill

I am on to my second set of sail drives, SD50T'S, the first two gave up after only 750hrs, the Yanmar "expert" couldnt explain why, there was no single problem with them but a whole range issues which rendered them no longer servicable or even repairable.
Symtoms leading up to the failure was extreme vibration between 1800 and 2400rpm ,much worse when Gori props where in overdrive.
Constant slipping of both clutches.
Continuous leaking of oil from top seal. Just to name a few that i can remember.
I allways had my suspicions that the Overdrive feature on the props may have been putting to much pressure on the allready fragile build of these units, but Gori and Yanmar deny this of course.
These days i just avoid using the overdrive feature just incase that was the problem, which is a shame because it is a great idea ,just maybe more suited to a shaft drive.

[DotDun]

All Yanmar saildrives I have played with (admitted only a few - SD20 & SD60) are left-hand props (CCW rotation).

[Captain Bill]

That's about the worst story I've ever heard about, not even repairable. I had one drive completely rebuilt at about 1500 hours. I had a little water in the oil for a prop shaft seal, and I overheated it trying to make a bridge opening. The water boiled and inverted every seal in the unit. It took me about a week to arrange a haulout, but all that time it had been full of seawater. They essentially replaced all of the guts. I could have gotten a new one for only $500 more but there was a 90 day wait for delivery. The rebuild only took two weeks.

[cruiz9]

Actually the mechanic said one of them was probably repairable but he could not guarantee how long it would last as he could not figure out what caused the problems in the first place, and since my insurance company where covering the costs { because Yanmar wouldnt} I went with the new ones. total cost including hardstand fees, around 20K.