YSM8 oil leak

[Atcowboy]

The YSM8 yanmar in my 1979 cape dory has started to leak oil near the cylinder head. It's a pretty small leak volume wise, I could just barely notice it on the dipstick. Up until this, every oil check showed no change in level.

Normally I wouldn't really worry about a 40 year old engine marking it's territory, but the oil pattern in the engine bilge makes me think it's being ejected under force. Some of it looks like a fine mist.

Any ideas what is leaking and should I panic?

[Atcowboy]

A little more looking, and I would say yes it's being elected under pressure. 2 of the three bolts for the exhaust riser are loose, one can be seen in the picture.

Question to me is, why is there oil in the exhaust?

[Wotname]

Maybe don't panic but it needs fixing as it's most likely to get worse.

I suspect the steel oil feed line has rusted through but maybe you just need to replace the copper crush washers at the banjo bolt.

Clean all the oil away and you should be able to locate the exact source.

[Wotname]

Originally Posted by Atcowboy

A little more looking, and I would say yes it's being elected under pressure. 2 of the three bolts for the exhaust riser are loose, one can be seen in the picture.

Question to me is, why is there oil in the exhaust?

OK, just saw your second post. Tighten up the exhaust to confirm if an exhaust gasket leak is the source of the oil or not. Is there any other evidence of an oily exhaust?

[Atcowboy]

Originally Posted by Wotname

OK, just saw your second post. Tighten up the exhaust to confirm if an exhaust gasket leak is the source of the oil or not. Is there any other evidence of an oily exhaust?

I don't really see any blue when the engine is running. The last time I ran it was for a while and the engine bay smelled a little. That banjo bolt honestly looked like it had a drop of diesel coming off it. Plan is to clean it all up tomorrow and try to locate the leak. If it is a thinning oil return line, that's pretty high priority. I guess if it's just a leaking valve, that isn't so bad....

[Wotname]

A wild guess - oil leaking from rocker cover and then gets blown around the engine by leaking exhaust gases.

[Compass790]

Yea locate the leak. My advice is to use threadlocker on every nut & bolt every time on these noisy shakey beasts.
I reckon Wottie could be right that exhaust leak is blowing the oil around. Leak could be coming from head gasket or rocker cover or oil pipe or its banjo bolts. That oil pipe supplies the oil to the rocker arms after it exits the main bearings so its important tho your oil pipe doesnt look as rusty as ours did.

Please report back what you discover, following with interest.....

[Atcowboy]

Well, I'm hoping that it is fixed. I cleaned it all up and was able to look at the exhaust valve and don't really think it's coming from there. The banjo bolt felt a little loose, so I snugged it up. If it continues to leak, I do have spare crush washers. I put a wrench on the valve cover bolt, and it felt sufficiently snug. My guess is that some kind of vacuum/vortex was made by the exhaust gases and it drew the oil leak towards the exhaust leak. It had wicked it's way in-between the riser and the block/gasket.

I found a raw water leak to fix and changed the thermostat like we talked about months ago, inspected the zinc. It's only been running for 30-40 minutes, but I don't see any more oil. It still is only about 40°c though (higher than idle to produce as much current as my flat batteries will take).

- AT

[Compass790]

haha an oil leak described as a 40 year old engine marking its territory! Luvd it.

Give the japanese some credit, they took a 1930's pommy engine design & somehow manufactured it without oil leaks. Mind you the YSM8 has some japanese mods.
Anyway dont ignore any oil leaks on yr YSM8, it shouldnt have any amazingly enough.
I'd paint that oil line if I was you. Its not very thick walled & you'd hate it to blow from getting corroded.
Ours got badly corroded by a head gasket leak spraying hot salt water on it.

In our experience the ysm8 will not get up to operating temp unless it is driving the boat. The dinky little Hitachi 35 amp alternator with its thermal cutout will not load it up enough to heat it up. Even our 55 amp Bosch that runs continuous wont heat it up fully IIRC. Funnily enough I had the same banjo bolt & exhaust leak problems as you fairly recently but that was because I never tightened the banjo bolt properly after being distracted & I put anti seize on the exhaust bolts instead of threadlocker. Ha, the ysm8 laughed & shook the exhaust loose fairly quickly.
Thanks for posting back & glad your engine problems were minor.

[Atcowboy]

Originally Posted by Compass790

haha an oil leak described as a 40 year old engine marking its territory! Luvd it.
Anyway dont ignore any oil leaks on yr YSM8, it shouldnt have any amazingly enough.
I'd paint that oil line if I was you. Its not very thick walled & you'd hate it to blow from getting corroded.

I'll at least keep things lightly oiled for the time being, don't know when I'll get a chance to paint it.

I've been continually surprised that fasteners aren't seized on this old engine, I've never experienced exhaust bolts loosening. In my experience, they require persuasion to come out. Then I realized, besides the cooling galleries this engine is really in a much better environment than the car engines I'm drawing my experience on. Living in NE they get a yearly and lengthy salt water spray where as if I keep my systems working properly on the engine and the boat, this one is protected from the elements completely. So, I'll keep doing what I can to keep it in good trim, control the leaks, etc. It's a nice feeling having a reliable iron jib.

- AT

[Compass790]

I'd never experienced exhaust bolts loosening either, quite the opposite, hence the anti-sieze but I may not have tightened them enuff when I installed the new ss exhaust manifold due to access & hand weakness from a medical problem.. Its easy enough to take the oil line off & paint it but can understand wanting to wait till you can do the whole engine. Oiling it should be fine. In my case i was too scared to wait till repaint time as it was looking very dodgy. I ended up re-inforcing the oil line as well as painting. I cant imagine what a new one would cost in NZ but the $136 cost for the 6" fuel line from the lift pump to the eng. fuel filter gave me a clue that it would be more than I would want to pay.
People would say its mad risking the oil line failure & i wouldnt argue with that but I'm confident in my repair. Oil pressure warning squeal is real loud if I'm overconfident! lol.

[Atcowboy]

It doesn't look like it's lost much of it's meat, to me. I'm just in the process of a sobo trip down the east coast of America right now so painting will have to wait some amount of time. Even then, it looks like it's brazed together. A resourceful person could likely disassemble and create anew. The fitting by the banjo looks like it has the beef to essentially be permanent.

-AT

[Wotname]

Originally Posted by Atcowboy

It doesn't look like it's lost much of it's meat, to me. I'm just in the process of a sobo trip down the east coast of America right now so painting will have to wait some amount of time. Even then, it looks like it's brazed together. A resourceful person could likely disassemble and create anew. The fitting by the banjo looks like it has the beef to essentially be permanent.

-AT

I agree. FWIW, there are three banjo fittings on the oil line - one at each end and one in the middle.

[Compass790]

Originally Posted by Atcowboy

It doesn't look like it's lost much of it's meat, to me. I'm just in the process of a sobo trip down the east coast of America right now so painting will have to wait some amount of time. Even then, it looks like it's brazed together. A resourceful person could likely disassemble and create anew. The fitting by the banjo looks like it has the beef to essentially be permanent.

-AT

Yea you'll be right, ours was in a lot worse shape than yours & it still didnt blow. I would have made a new one out of ss tube if I was in my last job.
Relax & enjoy your trip to warmer climes.

[Atcowboy]

Originally Posted by Compass790

In our experience the ysm8 will not get up to operating temp unless it is driving the boat. The dinky little Hitachi 35 amp alternator with its thermal cutout will not load it up enough to heat it up.

So after about an hour of motor sailing, the thermostat area was still around 40°c. The oil line where it comes out the top, that was about 60°c. With WOT for about 5 minutes, 44°c/78°c

- AT