I thought I'd post this for the benefit of anyone with a 1, 2 or 3GM or similar engine.
I had read in this forum of the known problem of rusting and failure of the little lube oil line that runs from beneath the starter around to the rear of the cylinder head, but hadn't looked closely at mine.
Just over a week ago, after pulling into Port Fairy's safe harbour I thought I'd better check things like engine oil, bilge level etc. Many short epithets came from my lips when I discovered the rear of the engine coated in oil, sump level down to lowest mark on the dipstick, and the bilge contents a deep black colour.
I managed to trace the leak to the pipe and removed it, to find it had a small hole around midway along. Bad enough, but then it almost fell in half as I handled it. So how lucky was I that it hadn't broken through and quickly dumped all the oil the previous day while I was out there in 25 knots motoring to safety?
To add to my great fortune, the local bush mechanic who services the Port Fairy fishing fleet diesels was around and brazed the banjo's onto a bit of tube for me in under an hour. This all happened just after Christmas, so I avoided having to wait a week or so for the dealers to reopen and ship one to and charge me the horrendous Yanmar OEM price.
So here's a shout out to Andy Gilmore ("Gilly") the bush mechanic in Port Fairy, look out for him if you need repairs.
And here's a strong prompt to all you GM owners to take the pipe off and inspect it, and probably replace the little sucker anyway.
And here's to the great sea-god who wasn't quite hungry enough for my life on that particular day. Mind you he or she managed to give me a comprehensive arse-kicking on the way back from Flinders Island over the last few days!
Cheers, Graeme
Thanks for the heads up ! ..........that is a hidden spot ! ....... I just went and ad a look .
Not entirely isolated to Yanmars.
My Bukh dumped half it's oil into the bilge when the external oil line rusted through. We were on a passage and I was lucky that my partner noticed the oil seeping from under the engine cover when she went below for a drink. I could have ended up with a new expensive anchor. 
A trip to the local hose supplier, and I had a new one on the engine the next day.
On the bukh DV 20 BW6 gear box it has a external dipstick tube which after many years of engine vibration tend to crack near the lower banjo bolt then the oil runs back to the rear gear box seal and tends to make the fixer upperer think the seal is leaking which it's not.( its a tight spot to see and to get to in a boat
I've removed my dipstick tube completely and use my own level plug taped and drilled into the gearbox side slightly higher than the one the gearbox has which can be used on other applications for the gear box
Select to expand quotewongaga said..
I had read in this forum of the known problem of rusting and failure of the little lube oil line that runs from beneath the starter around to the rear of the cylinder head, but hadn't looked closely at mine.
That pipe sounds like it is feeding lube oil to the overhead rocker gear, which while critical, it is not near as critical as the similar pipe on my Yanmar 2 QM 15.
The pipe is between the filter and the main oil gallery feeding the crank shaft. If it was to let go I think it would dump all the oil in a few seconds.
The pipe is copper but the banjos are steel and will rust. I can't remember if I was able to find brass banjos or not but I did remake the whole thing with new parts and have cleaned up the old one to keep as a spare.
