[Minnewaska]

I can't swing a larger or higher pitch prop as it would not reach 3200rpm. I forgot to mention I've a 2 blade 15"D x12"P Flex-O-Fold as well. Max it could make is shy of 3300rpm.

I had to look it up. Your motor's max rpm is 3600 (continuous max is 3400). Cockpit tachometers are notoriously incorrect by 100-200rpm, but when you're below the target by more than that, you are very possibly over propped. It is also possible that your tach is off in the other direction and you're even more over propped than that. Best is to text your wide open throttle rpm under way with a calibrated test tach attached to the motor.

So far all checks and feels points to rings wear. Compression test seems to confirm that. Anyhow, I'll try the "Warm" and "Wet" test and post results here. Unfortunately, test analysis of crankcase oil isn't common or known here.

You can mail your sample away for an oil analysis. While I think they are good idea, they are more valuable when you do them over time and can see trend lines changing.

Are you seeing any smoke from the exhaust? If your rings are as shot as you suspect, I would expect notable smoking. If so, what color?

 

[Minnewaska]

How come no answer to the color of the exhaust smoke, if any?

 

[Minnewaska]

A little white smoke at start up, followed by zero smoke after warm up is a fairly normal condition. I would have expected blown rings to have some blue smoke, especially under load. The black smoke after jamming the throttle is also very normal. You introduce fuel faster than combustion can increase, so you get a good belch of unburned fuel. Ignore that symptom.

The sheen on the water is a bit tougher to diagnose without seeing it. Both oil and diesel will leave a sheen. Even coked up diesel soot in the exhaust that is just being washed out by cooling water could cause it.

 

[Minnewaska]

I still would not rule out the prop. It's documented above that she does not make max rpm. An engine has to be awfully sick, which would have some severe starting, smoking, knocking, etc, issues before it would fail to do so, without the prop being a problem.

I find the gear reduction ratio to be very unlikely, unless this was changed over the years.

 

[Minnewaska]

That's not much coolant loss, perhaps even just normal heat expansion/contraction.

If you are eating coolant, a bad head gasket is often to blame. Curiously, that could also account for poor compression tests. However, you would probably see more loss, if all cylinders were leaking and you typically see some milky substance on your oil dipstick.

You can have your cooling system pressure tested, which would be a simple task and good idea. You may also see oil or coolant seeping from the gasket line.

If it does turn out to be a head gasket, you will want to consider how it may have occurred. Over heating can warp the head, excess power settings or using starting fluid can put too much pressure on it.

 

[Minnewaska]

A diesel needing an overhaul at 1,550 hours over 12 years, without being abused or severely overheated, is about as common as a 30 year old getting Alzheimer's.

While it is most common for coolant to leak into the engine oil and cause the milky telltale, if the gasket leak is near a higher pressure location, the oil can leak into the coolant instead. Since it hasn't been changed in so long, I would drain it and take a look.

 

[Minnewaska]

......within 2 years I choke up the U Mixing Elbow with enough coke & rust to stop the engine running. Got engine fixed in workshop. Shouldn't have to actually. As I learn more of diesel, I guess I got careless/complacence. 3 years back discover only about 1 litre oil in engine after a 500nm passage........

:laugher well, goodness. That's a problem. Would have been useful to know.

 

[Minnewaska]

Being over propped could be what coked the elbow up in the first place.

 

[Minnewaska]

and....... if the OP doesn't figure out how to get the WOT rpms back to the proper level, this may all repeat itself. Without that fixed, every other suggestion is temporary.

 

[Minnewaska]

According to Mr. Google, your motor is rated at 3400 rpm for continuous use. That's just the rpm you should not exceed for lengthy periods. Wide Open Throttle rpm should be 3600 rpm. It really sounds like you've been over propped for a long long time, if these were the rpms you were getting years ago. If you don't correct that, things will get worse and your repairs with be for naught.

However, clogging the exhaust elbow to the point of stoppage and running the oil low for 500 nm had to have done some damage. It's just hard to tell what exactly. I would even wonder if water flushed back into the cylinders with that elbow stoppage. However, other than the low compressions, you have no unusual starting, smoking or noises. That either defies reality or is a testament to just how tough these motors really are.

With the limited experience you describe, I suppose it's possible you don't know they are unusual and it might be wise to get someone aboard to take a look/listen to help you diagnose.

Good luck.

 

[Minnewaska]

More like 10ml

Did you buy a compression gauge?

 

[Minnewaska]

Yes, I bought a diesel compression gauge. US General.

Is that the US General line that is carried by Harbor Frieght? Probably okay, but I would at least be a tad suspect, if it is. Be sure the adapters are correct and seat properly, or the reading could be wrong.

 

[Minnewaska]

It seems pretty unlikely there is nothing wrong with a motor whose mixing elbow was coked and rusted up so much that it choked the engine off and was then run for a long period on 1 qt of oil.

Nevertheless, if it is okay, it is stated the motor will not make max rpm under load. If that's all true, it has the wrong prop. Failing to correct that will cause engine damage.