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Old 03-26-2013, 06:12 PM   #239
Marin
Scraping Paint
 
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The sheen on the water has zip all to do with your oil. It is unburned fuel. Old generation diesels, like Lehmans, are relatively unsophisticated. As such, when they are cold they cannot burn all the fuel that is fed to them so the unburned fuel goes out the exhaust and is what creates the sheen behind your boat while the engine is warming up.

Assuming the injectors are good and so on, the sheen will go away as the combustion chambers get up to temperature. The sheen will also be greater in cooler weather than in warmer weather as the engine itself will be colder when it starts.

A good friend who for decades was the head of the engineering department at Alaska Diesel Electric aka Northern Lights/Lugger told me that eliminating the excess of unburned fuel when a diesel is cold is one of the hardest things to deal with in an engine, but environmental regulations required it. As he explained it, this is one of the things that hastened the development of electronically controlled diesels.

But with a Lehman and other similar old engines it's just the nature of the beast. And it's got nothing to do with oil.
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