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Salts in the oil

7293 Views 73 Replies 25 Participants Last post by  tankersteve
Here I sit in a marina in France BR's engine in pieces. Why, you ask? Salts in the oil.

Prior to the trans-lant last summer I re-powered the boat. Out went the 18 yr old 55 hp Nanni, in came the new 110 hp Yanmar. (Note the boat's designer indicated we needed at least 90 hp, so the first owner obviously underpowered her.)

As we will sell the boat sometime in the next 5 yrs or so I decided to have an oil analysis done with each oil change. I took a sample at the 50 hr oil change in Newfoundland, and another when I laid up the boat in Scotland last September at 280 hrs. I forgot to take the samples home with me and the first opportunity to send them to the lab was in the luggage of a departing crew member several weeks ago.

Lab reports came back: first oil sample had small amounts of sodium and potassium in the oil. The lab was curious. The second sample (taken at 280 hrs) showed a very large increase in the amount of sodium (5200 ppm) and a similar increase in the potassium. Lab said -- no doubt something is leaking into the oil. They said it could be seawater, or it could be coolant. "Find the leak" was their recommendation. Salts in the oil were causing accelerated wear of critical bits of the engine -- and the metal content of the oil samples was also well above normal.

I'll stop here for an important digression: without the oil analysis I would have never known this was going on. The engine runs perfectly, aside from a bit of soot on the transom. I would have continued motoring along (when not sailing) fat, dumb and happy and, because I plan to sell the boat, it would have been the next guy's problem because the excessive wear of bearings, etc. would probably not shown up as a real problem for a while. But I do have the oil analysis and so it's my problem. :(

So, the question is what to do?

First step was to call the Yanmar guy here in Brest, France. He's a nice man in his late 50's (that's good -- means he's experienced), and he speaks some English (that's also good because I have only high school French and a copy of "French for Cruisers").

He comes aboard last week and the first thing he does is take another oil sample. His examination of the oil on the dip stick and inside the valve cover suggests to him that it's not water. He said, "The oil is beautiful". First time I've heard someone call dirty 150 hr engine oil "beautiful", but this is France and things are different here.

So far we have removed the oil cooler and pressure tested it on the bench at 80 deg C. It's good, no leak there. The oil analysis requested last week came back today and we continue to have sodium and potassium at elevated levels. So there's a leak somewhere.

The question I have for the gathered mechanical cognoscenti is what course of action do you think we should follow from here? What are the potential sources of a leak of either seawater (minimal probability) or coolant (likely) leaking into the oil.

All though I have confidence in Philippe, our local Yanmar guy, your sage advice will be welcome.

I will conclude by saying that it's true -- cruising is defined as working on your boat in exotic places. While Brest isn't exactly "exotic" the food is very good, the cheap wine very good, the bread excellent and the cheese very smelly. What more could you ask for? :D

PS -- I forgot to mention: we had an overheating incident at 10 hours when the main alternator belt came off while motorsailing. Engine was shut down immediately (like within 10-15 seconds of the alarm), but the temperature gauge indicated 250 deg F / 120 deg C. Motor has worked flawlessly ever since. And I should add, we have had no over-cranking incidents -- the engine starts immediately, as a very expensive Yanmar should.
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IMHO, if the head gasket is failing, my main worry would be exhaust gases leaking into the coolant - as this can cause erosion damage of the cylinder block or head. I had to repair the head gasket on a Toyota car, and the leaking exhaust gases had cut a channel about 1mm deep in the alloy head. It had to be TIG welded and then skimmed to repair.

You can easily do a chemical check for exhaust gases in the coolant. They sell kits quite cheaply.
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It does occur to me that there must be some small salt content in the air that's taken into the engine for combustion, given that at sea, salt is everywhere. Could it be contaminating the oil that way?
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