[C320-list] My Yanmar 3YM30 Engine Dumped it Sump Oil in the Bilge

[Ian Neale]

I am new to the Association and wanted to let folk know of a recent issue with my Catalina Yanmar 3YM30 engine.

Recently when anchoring I noticed a significant amount of oil on the cabin floor.

On investigation I found about 1.5 litres of oil had been emptied from the sump into the engine bilge and floor area.

The engine was still running fine when we noticed the issue and we duly shut the engine down and then began a clean up of the spilt oil when we discovered what looked to be a cut off dip stick lying in the bilge amongst the oil.

I rang my Marine mechanic who told me of an issue with a rubber bung coming out of the Yanmar engine, I then did a Google search and found a blog on the Cruisers Forum describing the exact scenario I was dealing with.

The 3YM30 engines apparently have two oil dipstick holes in the block and Yanmar simply put a cut off dip stick in the dipstick hole they don't use to seal the block and sump off.  Over the years, my boat is a 2007 Mk II, the rubber plug on the cut-off dip stick hardens and shrinks, then if the engine moves on it’s mounts as mine did when anchoring it can fall out.  The engine then promptly empties your sump into the engine bilge area!!!!

Once the engine had cooled down I reinserted the plug to find it very loose in the hole, it was clearly loose for some time and it was simply a matter of time before it fell out.

This plug/cut off dipstick can be found in the block to the left of the oil filter at about the 4 o’clock position, not an easy spot to see it.

I think anyone with the Yanmar 3YM30 engine should check this plug because depending when and where it decides to fall out the consequences could be disastrous.

The link to the Cruiser Forum blog is as follows, it provides a photo of both the cut off dipstick and the hole in the block where it goes: https://www.cruisersforum.com/forums/f54/yanmar-3ym30-dumps-oil-into-bilge-149455.html <https://www.cruisersforum.com/forums/f54/yanmar-3ym30-dumps-oil-into-bilge-149455.html>

Ian Neale

Solutions Hull #1122

New Zealand.