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I'm using a Volvo Penta Propeller Shaft grease to to lubricate and seal the propeller shaft in my boat. The grease eventually gets "squeezed" out from the various lubricated spots and ends up in the keel. The grease gets pumped out into the ocean every now and then along with any water which may end up in the keel as well.

Is there any reasonable biodegradable alternatives for shaft grease which are good - or would salt water kill the sealing properties of a biodegradable alternative?

Grease is insert into the "cup" sitting on top of the shaft, and it slowly "exits" along the "blank" shaft to the left - and then falls down.

enter image description here

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  • I don't have a definitive answer, my instinct is that anything biodegradable won't last or perform well enough for that function. – GdD Dec 14 '20 at 12:01
  • I'm surprised there's no seal on the shaft to keep the grease in ... it'd be hard to replace when needed, but if greased, it'd last quite a long while. – Pᴀᴜʟsᴛᴇʀ2 Dec 14 '20 at 12:07
  • Updated post with image. This boat (or inboard engine) isn't by any means new - it's from the mid 70's. Maybe things were done differently then, but the grease does slowly follow the shaft and then eventually drop down into the keel. – sbrattla Dec 14 '20 at 12:37
  • There is a seal - the plate with the two bolts holds it in... But check with grease manufacturers - they do marine grade stuff so if anyone knows they will. – Solar Mike Dec 14 '20 at 12:39
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A good research clue would be "OSPAR compliant stern tube lubricant"

I found also that Klüber has a good range for marine products.

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[Ultra Lube Biobased Grease]

https://www.amazon.com/dp/B002BVY9MG/ref=cm_sw_r_cp_apa_fabc_hJ81FbHJ4DNPR!

It says it's good for metal to metal, rotating shafts, etc.

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