Seeking "Best Practices" for Yanmar SD 50 Cone Slip

[psychfeld]

I'm including an email I recently wrote to a previous poster on CF back in 2012. I'd like to see if there's a more current thread or any new ideas about this problem.

It may be of interest to those with SD 50s to read about a quick fix I used that appears to have provided positive immediate, at least short term, relief of the slipping cone.

As usual, many thanks to those thoughtful contributors!

...here's the email:

Hi there,

I saw a posting with your email on CF dated in 2012. I've got a 2009 Lagoon 420 with two SD 50's recently purchased 9 months ago.

At month 8 one of the SDs started slipping. Stuck a long ways from home a mate suggested i replace the gear oil (I'd been using the Quick Silver, High Performance Lube from MercCruiser) with diesel motor oil 15-40.

I followed his suggestions given my predicament - new owner/operator, not skilled at navigating this cat on a single screw. I took the chance that further damage might occur and pumped out the old lube for 15-40 (I don't believe there is any damage, I've been running without slippage for another 40+ hours since swapping lubes).

To my surprise since swapping the gear oil in the slipping SD the unit has performed without slippage (at least I cannot detect it as I could before). Upon further online investigation of options I see the Yanmar replacement SD 60 no longer suggests this overpriced gear oil but instead authorizes diesel motor oil 15-40 as the recommended lube.

I would love to hear any suggestions you might have to remedy this apparent chronic problem - under no circumstances should this unit be serviced with cone removal/scoring every 500 hours - please advise the experience, conclusions with your thrust bearings. I am eager to find an intelligent repair!

Best regards,

Rob Phillips