SD External Oil Leak At Startup

[The White Whale]

I have a Hanse 370 from 2008 with a saildrive Yanmar SD50. I had the boat for 6 months where it sailed around 500 miles during which i never noticed any issues.

Recently the boat has begun to leak drops of oil into the water in its wake just after startup. Not much but enough to notice. The leak begins when the transmission is engaged and the boat starts moving and gradually decreases until about 3-5 minutes after when it stops completely - at least enough to make it unnoticeable. There seems to be a positive correlation between the amount of time since the boat last sailed and how much oil is leaked but i'm not 100% about this.

The SD oil level does not appear to go down and the oil remains clear and healthy. I have not touched the SD or its oil at any point besides inspecting the level and quality. The SD seals where replaced in 2019.

Any ideas, explanations and theories are appreciated. Thanks :-)

[Tin Tin]

The SD 50 has two seals at the prop shaft, a water seal and an oil seal. Maybe the oil seal it starting to fail first, it may also have fishing line or a groove starting at the shaft. It best best to change them each haul out, not particularly expensive, easy to do.

[The White Whale]

Thank you for the answer! I'll make sure to change the seals at next haul out. I presume it's not an urgent matter as long as the oil quality and quantity is good.

[GordMay]

Greetings and welcome aboard the CF, White Whale.

Fixing the Yanmar SD50 oil seals
➥ SD50 oil seal replacement

Yanmar Sail-Drive OPERATION MANUAL [SD20, SD50, SD50-4T]
➥ https://www.yanmar.com/media/global/...OM_27MAR09.pdf
➥ https://j109.org/docs/yanmar_sd20_sa...operations.pdf

Yanmar Sail Drive REPAIR SERVICE MANUAL [SD40/SD40-4T, SD50/SD50-4T]
➥ https://filesmart.sellfy.store/p/fy5hpy/
➥ https://www.scribd.com/document/4178...ice-manual-pdf