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Xawdisney · 24-05-2023, 19:18

Pete: Just to clarify... I did run it from a bucket via the intake hose, not direct hose. Used to do that to winterize my raw water engine, to flush out salt, and to add antifreeze for winter. But in this flush just ran out the exhaust, not through engine at all. Until I added coolant the oil I removed was normal dirty oil... normal amount.

When I was running the engine in fall, it seemed ok. Wouldn't I have heard that bubbling or hissing at that time with engine running? I would believe exhaust valve considering gunk that had been in exhaust elbow, and the hose below was pretty much melted.

Bill O... Not an issue. Has not run since winter.

**skipperpete** · 24-05-2023, 19:41

I’m happy to hear that you did the bucket flush. I sold my previous boat and the new owner wanted to run the engine on the hardstand so he shoved a hose in the raw water intake and turned it on, climbed back aboard and started er up , all good. Then he shut it down but was way too slow getting back to the tap and the engine... via the exhaust filled up with fresh.
No, you wont be able to get sensible leakage test results by running the engine, you could see “blow by” but an exhaust or intake valve is difficult to detect unless its really bad. A head gasket should blow water out of the top tank but a perforated cylinder wall may not.

MicHughV · 28-05-2023, 04:45

The MD7 engine....being raw water cooled, has a tendency to clog up the water cooling passages around the cylinders. When I had my cylinder head off, I was stunned to see how clogged those passages were. I was amazed any water was able to pass thru' there at all, so certainly an area to check.

Taking the cylinder head off is a relatively simple matter.

Bill O · 28-05-2023, 05:10

Quote:

Originally Posted by MicHughV

The MD7 engine....being raw water cooled, has a tendency to clog up the water cooling passages around the cylinders. When I had my cylinder head off, I was stunned to see how clogged those passages were. I was amazed any water was able to pass thru' there at all, so certainly an area to check.

Taking the cylinder head off is a relatively simple matter.

Agree good to take the head off to inspect the gasket.

Agree clogged passages can happen with raw water/salt water cooling and they should be checked periodically or descaled w/a cleaner.

Not certain the clogged raw water cooling passages would make it leak antifreeze in the oil though.

JimsCAL · 28-05-2023, 05:40

My previous had a Universal 5411 which was raw water cooled and I had many of the issues you are dealing with. The overheating is certainly pointing to the head gasket as being a strong candidate for the the problem. The engine driven pump is also a possibility. The pump on my 5411 had a weep hole in the casting between the 2 seals so you could tell if either the oil or water seal was leaking. But that amount of coolant in the oil is huge. It should be easy to find the cause.

NNBill · 02-06-2023, 10:47

Another possible location, these engines have wet cylinder liners. There is an oring at the bottom of the liner sealing between the liner and cylinder assembly.