Leaking Yanmar 3GM30F and sheen in exhaust

[bsangs]

I feel my 35-3 is angry at me this year. After a few years of relatively easy maintenance that didn’t require too many Boat Bucks, she’s trying to bankrupt us. It’s like she knows my wife is planning to retire and is giving us a, “Not so fast, my friend.”

The latest is a leaking Yanmar 3GM30F. It’s dripping below the engine about once every 20-25 seconds. Even more alarmingly is the sheen of what I assume is diesel emanating from the exhaust, though it seems to only happen at lower RPMs. Gives off a little white smoke when she starts as well. I’ll be damned if I can locate the leak. It doesn’t reach the bilge, thanks to the absorbent pad I keep below the engine. The engine runs fine, but it’s obviously problematIc. Last year I replaced the exhaust elbow, had a bleeding nut replaced. This year I replaced the cooling water hose from the strainer to the engine. None of these show any evidence of leaking.

Any experts have thoughts about this? And what’s the best practice for detecting a leak when you simply can’t see it searching around with a flashlight?

 

[EricD.]

Check the oil pressure delivery line that wraps around the back of the engine to the starboard side. I had to replace mine a year or two ago. I understand it's a common problem.

 

[bsangs]

Check the oil pressure delivery line that wraps around the back of the engine to the starboard side. I had to replace mine a year or two ago. I understand it's a common problem.

Will do. Did you get an oil pressure alarm when that was an issue? (I’m not getting any alarms.) And diesel leakage was an issue with this?

 

[Prairie Schooner]

To clarify, what's it leaking? Oil, diesel, raw water, coolant?

 

[bsangs]

To clarify, what's it leaking? Oil, diesel, raw water, coolant?

It’s diesel Jeff. Without question. (Smell and taste confirmed. )

 

[Puget sailor]

If you have a fuel drip and running issues check all the fuel line banjo bolts and hoses coming into the on-engine fuel pump and between that pump and the on-engine fuel filter etc. It’s very cramped spacing, and I was working with a friends 3gm30f, and found one of them to be barely finger right. Lots of vibration can loosen them. If air gets pulled in, the engine can run funky and make smoke etc. if you can’t get a good look easily, try using your phone to record video with its light on and then review it. It’s possible with an iPhone to shoot video with the light on continuously by swiping up on the camera shooting choices text (photo, video, etc) and it will reveal the flash icon which can be set to ON, which for some reason is only possible in video mode. I use it all the time for stuff like this.

Another possibility to be concerned about is the fuel pump diaphragm can develop a pinhole which can lead to diesel in the engine oil, and possibly air getting sucked into the fuel flow, also causing running issues. See if the engine oil smells of diesel it seems unusually thin.

And check all the fuel pipes for leaks or loose connections going to the injectors, and the return hoses, but the pump and filter side seems to be the more likely culprit, and harder to get a good look at too, depending on you engine layout.

 

[bsangs]

If you have a fuel drip and running issues check all the fuel line banjo bolts and hoses coming into the on-engine fuel pump and between that pump and the on-engine fuel filter etc. It’s very cramped spacing, and I was working with a friends 3gm30f, and found one of them to be barely finger right. Lots of vibration can loosen them. If air gets pulled in, the engine can run funky and make smoke etc. if you can’t get a good look easily, try using your phone to record video with its light on and then review it. It’s possible with an iPhone to shoot video with the light on continuously by swiping up on the camera shooting choices text (photo, video, etc) and it will reveal the flash icon which can be set to ON, which for some reason is only possible in video mode. I use it all the time for stuff like this.

Another possibility to be concerned about is the fuel pump diaphragm can develop a pinhole which can lead to diesel in the engine oil, and possibly air getting sucked into the fuel flow, also causing running issues. See if the engine oil smells of diesel it seems unusually thin.

And check all the fuel pipes for leaks or loose connections going to the injectors, and the return hoses, but the pump and filter side seems to be the more likely culprit, and harder to get a good look at too, depending on you engine layout.

Thank you. So in a couple of those instances, it sounds like the engine wouldn’t be running well, correct? I ask because we had her out yesterday for nearly six hours running the engine - doing some maneuvering practice - and it ran without issue.

 

[Afrakes]

Thank you. So in a couple of those instances, it sounds like the engine wouldn’t be running well, correct? I ask because we had her out yesterday for nearly six hours running the engine - doing some maneuvering practice - and it ran without issue.

One of the best investments I've made is an inexpensive borescope. It allows me to see things directly and has helped me solve engine leaks on friend's boats. Especially big power boat engines with really tight engine compartments. Sometimes a mirror and a bright light just aren't enough.

 

[Pete the Cat]

I would use some spray cleaner and paper towel the engine down to get all the current diesel off all the connections. Dry everything over night and then run the engine for a bit. I might also put some paper towels in strategic places after the lift pump (nothing is pressurized before that) just to see if I can narrow the leak area down. I agree with the utility of the cheap endoscope--I have one with a side camera and front camera and split screen--I think I paid $60 for it and it has been very useful. Diesel engines belch a little white and sometimes blue smoke at start up that you might not normally notice. The white smoke can be simply condensate from the cooling of the systems the last time you ran it and the blue smoke can be residual diesel as all diesels stop with shutting off the air so there is a bit of diesel that can be left in the chamber. You might have a dripping injector, but before you start replacing stuff, I would rule out a simple leak somewhere and not worry too much about the smoke. FWIW.