It seems that this is a common problem with the Kazaki cone transmissions.
What happens is that the cone gets glazed/polished and thus loses grip. The solution is to dismantle the transmission
, and then remove the glazing by grinding the cone with a lapping compound - the same paste stuff that is used for lapping engine valves so they sit properly in their beds.
It is, apparently, not a difficult job. Unfortunately, we were unable to dismantle our unit owing to a previous issue with it which had been resolved by someone putting locktite onto the drive shaft (another long story).
We have, in fact, only just had someone take the unit apart for us and do the repair job. It just us 200 euros in Sicily
so, as you can see, it is not a big job provided someone knows what needs doing and doesn't talk you into buying
a new gear box!
Until now we have been managing by changing the oil
regularly, which certainly did help.
Curiously, having now had the job done (he says it has previously been done also) the mechanic
is recommending we use ATF fluid, instead of the normal SAE 30, for this gear box. Seems odd, but he since he did the repair he must know what he is saying ,so we shall see. Since we are wintered now, we haven't tested it out properly, but it seems to be working much better when we tried it out at the dock
If you have a Yanmar SD50 saildrive
, there is a document from the Lagoon
owners forum that describes exactly how to do the repair. I don't know if I can share that publicly, so pm me if you need the link.
Hope that helps.