Importance of the stern tube greaser

I’m just passing along our experience, in case someone else goes down this same path.

When we bought Rainshadow, the PO told us that there was no need to use the stern tube greaser anymore – that he had a marine mechanic replace the shaft packing with dripless packing seal, so the grease was no longer required – though he sometimes still did use it out of habit. (Receipts show he made this packing material change about 10 years ago.) Being niave, we believed him and so did not use the stern tube greaser. We adjusted the packing gland as needed based on the drip rate.

After about 1000 NM of sailing last year, by the end of the season a THUMP-THUMP developed in the aft cabin. Our first thought was a fouled prop. But we eventually traced it down to the tail shaft being too loose and when sailing with the prop free to spin, it can hit a resonance so it Thumps somehow in the stern tube. When at rest, we can recreate the sound by wiggling the tail shaft. So we figured it must be time to replace the white metal bearing. That’s when we discovered that the stern tube greaser is ALSO for the benefit of the white metal bearing lubrication – not just the original flax packing. So that marine mechanic who said the stern tube greaser was no longer required didn’t understand about the unusual white metal bearing arrangement.

For our first sail this year, we used the stern tube greaser heavily, and happily the THUMP-THUMP is gone. It was lovely wind, and we went through a range of sailing speeds from a few knots up to 7.2 knots – and no THUMP the whole time. (The tail shaft is still too lose according to the wiggle test, so we probably still need to change it – and I think we’ll go with the composite bearing as described in my other post.)

The morale of the story – the stern tube greaser is important if you have the original white metal bearing. Don’t forget to use it as described in the manual.