Yanmar 4JHE oil pressure collapse.

[sand6000]

Today my 26ft launch stopped suddenly at 2500rpm and on checking there was a large amount of oil in the bilge and the Oil Pressure warning light was on. Put 3L of new oil in and managed to limp back to the marina at 900rpm and now wondering where to start. Engine has 1700 hrs. Any help please. Pat


Forgot to mention. Oil seems to be from rear of engine.

[a64pilot]

Well, run it and find the leak, of course run it with oil in the crankcase.
Do you have a remote oil filter?
Rear of engine sounds like rear main seal, but not necessarily. I asked about the remote oil filter cause I had one and the adapter blew the O rim out and leaked badly.

[scotty c-m]

Start with a flashlight and a rag. Use the flashlight to inspect every inch of the motor. Sometimes the problem will be right in front of you. Use the rag to clean every bit of the motor. Fill the oil up and run it at low RPM. Any oil leaking - or pumping - out?

[Oc1]

A mechanical oil pressure gauge if it has one could be the problem. I've seen several develop holes in the feed lines. They will pump a lot of oil out of your engine quickly.

[paulie4203]

I had the same issue once. The pressure sending unit either fell or broke off sending all the oil into the bilge. It's located on the left side of the engine if looking at the front of the engine, about in the middle fore and aft, front to back. Good luck.

[Vasco]

The oil coolers in the 4JH don't have anodes and rust out real fast.

[Calif.Ted]

The GM series had a metal oil line on top of block that sometimes corroded when exposed to minor leaks etc at rear of engine.

[Squanderbucks]

If you run an engine without oil even for one minute it is pretty much toast. By cranking it back up and continuing to run with zero oil pressure you should expect the worst. May need to do a full rebuild - turn crank and new oversized beatings maybe pistons and rings etc. just finding leak and putting oil back in will not likely cut it. It may crank and run but not likely for long.

[Squanderbucks]

The fact that it already seized once is an indication how severe the original damage is. After cooling down it would restart because of the contraction of metals and the massive torque of diesel starters. I’ll bet that if you did an oil sample even on your added oil the metals would be off the chart.

[a64pilot]

Originally Posted by Vasco

The oil coolers in the 4JH don't have anodes and rust out real fast.

I hope not, cause mine is 30 years old.
It certainly is at the back of the engine though.
I assume when one goes it leaks oil primarily to sea water?
Got me thinking though maybe it’s time to retire mine.

[Vasco]

Originally Posted by a64pilot

I hope not, cause mine is 30 years old.
It certainly is at the back of the engine though.
I assume when one goes it leaks oil primarily to sea water?
Got me thinking though maybe it’s time to retire mine.

I took mine off for a look because a buddy's had gone. When I cleaned it up it was paper thin! Replaced it. I would take a serious look at yours. I got a Yanmar one $600 or maybe a bit more, can't remember but it was a lot. But there are aftermarket ones available.

[Crusty Joker]

OK, this may not sound like a direct answer to your question, but be thankful that the engine is small. It is a SMALL problem.
Great engine that still runs after 30 years!

After you disconnect everything, starting with the battery... and secure the shaft so the hole does not sink the boat...

Nice thing about little engines is that they can be lifted out using the halyard. Put it in a shopping cart and take it up the gangway to a repair guy. Not a cheap guy but someone who knows the engine and can fix it properly.

Test it before you take it to him by running it on the bench or garage floor with oil in it... make sure it is at idle with you start it...

I have lifted engines out of difficult places using the halyard and cardboard several times. Difficult is as difficult does. Attitude. Respect.

You made it home! GOOD sailing!

OLD UNCLE...

[westwinds]

Diesels have high compression so the bearing get destroyed very quickly without oil. Also, pistons can overheat without oil spray on the underside causing the engine to suddenly quit from friction. If you try to use the engine without taking it apart to see what problems there might be, you could cause further damage like a connecting rod through the side of the engine block. Here is a link to more information on what to look for: Overheated Diesel -- What Damage to Look For? - SailNet Community

[sailorboy1]

Originally Posted by Vasco

The oil coolers in the 4JH don't have anodes and rust out real fast.

A web search doesn’t appear to support this as an issue in general. While I don’t doubt it can rust out it doesn’t appear to be common to occur.

[sand6000]

Originally Posted by a64pilot

Well, run it and find the leak, of course run it with oil in the crankcase.
Do you have a remote oil filter?
Rear of engine sounds like rear main seal, but not necessarily. I asked about the remote oil filter cause I had one and the adapter blew the O rim out and leaked badly.

Standard filter and problem seems to be from the filter seal.