Premature main engine bearing failure mystery
12-30-2016 | 09:38 PM
#22
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Joined: Oct 2013
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From: SF Bay Area
So I get that sending some oil through the bypass un-cooled will raise the overall temp of the oil as measured by the thermostats located at then end of the first remote oil line, but the highest temp was never in excess of 260 deg, usually closer to 220 (except for 3 or 4 times for short periods before I changed the coolers). That means oil temp was not an issue and I still say that recycling unfiltered oil through a new engine for 90 hrs will not destroy a set of main bearings. I'm well aware that marine engines are different animals than car engines, but as a reality check: 90 hrs X 50mph = 4500 miles.
12-30-2016 | 09:41 PM
#24
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From: Roanoke VA
No argument. But in this case neither filter are in the "cheap' category and even if they were, I believe that it would take something on the order of at least a couple hundred hours of completely unfiltered and unchanged oil to trash the bearings. In this case even assuming the bypass valves opened, the the oil was at least partially filtered and was changed very frequently. These reply's have given me a few ideas to explore, which I appreciate, but I still don't think I know what caused this. I don't expect that the answer will be solved by discussing it with a limited amount of info and no photos but your suggestions at least give me ideas to think about. Thanks-
12-30-2016 | 09:52 PM
#28
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From: yorkville,il
i have seen a few big blocks that suffered a bearing spin from loss of oil pressure,the ones the farthest from the pump looked the worst.also took one apart that totally smoked the mains but never spun one.when the bearing trash flows through the engine the party is over.
12-30-2016 | 10:05 PM
#29
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Joined: Oct 2007
Posts: 8,439
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From: yorkville,il
No argument. But in this case neither filter are in the "cheap' category and even if they were, I believe that it would take something on the order of at least a couple hundred hours of completely unfiltered and unchanged oil to trash the bearings. In this case even assuming the bypass valves opened, the the oil was at least partially filtered and was changed very frequently. These reply's have given me a few ideas to explore, which I appreciate, but I still don't think I know what caused this. I don't expect that the answer will be solved by discussing it with a limited amount of info and no photos but your suggestions at least give me ideas to think about. Thanks-
