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Old 03-29-2013, 01:22 PM   #322
Marin
Scraping Paint
 
City: -
Join Date: Oct 2007
Posts: 13,745
Okay, I have only one question that is relevant to me as far as I'm concerned on this topic.

Our boat is 40 years old. At this point our two FL120s have a bit over 3,000 hours on them. We have owned the boat now for 14-1/2 years. Assuming no debilitating health problems and assuming we don't buy a different boat, we anticipate owning and using the boat another 20 years. So we will be putting several thousand more hours on a pair of engines that have a reputation for a service life of 12,000 to 14,000 hours in recreational boat service. This reputation was built when running on the manufacture's recommended oil which is single weight conventional oil.

In the cases I am directly familiar with where an FL120 actually failed to the point of needing an overhaul, the causes were almost always due to a problem involving coolant or raw water. Cooling water/coolant circulation or level failures, blown head gaskets, water backing up the exhaust and entering one or more cylinders, extreme hot spots forming as a result of poor coolant circulation or an air pocket at the front of the Lehman exhaust manifold, and so on.

A retired acquaintance in the UK whose decades-long career was maintaining, repairing, and overhauling Ford of England diesels including the Dorset (base engine of the FL120) told us that the absolute number one killer of that engine is an overheat. The head, he said, is extremely susceptible to warping even after a short period of mild overheating. He is why we have a timer at the helm to remind the person driving to monitor the temp gauges and this has "saved" us on the couple of times a developing cooling problem prompted a quick shutdown before an overheat situation occurred.

So given all that, how would switching to synthetic oil at this point make one iota of difference (other than to our wallets) to the service we expect to get from our engines?

All the evidence points to the fact that if one of our engines does fail in the next 20 years, it will not be due to the lubrication "wear" of using conventional oil.

I have no interest whatsoever in the detaily armchair theorizing and speculation that has composed the bulk of this thread. I don't give a rat's ass about the ppm of zinc in this, that, or the other oil. I look at the service life of the kind of engine we have two of in our boat, a service life that has been conclusively proven by real engines in real boats since the early 1960s using conventional oil, and I don't see how a synthetic oil is going to benefit our engines at all in terms of extending their longevity. When they do die it will be for a reason that will have nothing to do with the kind of oil in them, assuming we change it and the filter regularly, which we do every 100-150 hours.

I'm not saying that synthetic oil won't benefit some other kind of marine diesel, particularly a new-generation one. We use synthetic in our two newest vehicles. But when it ones to boat engines I'm only interested in the ones in our boat and I'm not seeing any reason whatsoever in this thread that points to an increase in their service life or the performance and reliability we will get from them over the next 20 years if we run them on synthetics.
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