Join Date: May 2013
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Re: Yanmar hard starting question
Building a diesel without glow plugs is cheaper than building it with them. And since recreational boaters are cheap and tend to not use their boats in cold weather...It sadly makes good sense to build cheap engines without glow plugs.
It also would make sense to check the options for the engine oil. Most old manuals will spec a single-viscosity oil because motor oils weren't very talented 30 years ago. These days? Odds are you can use a good synthetic, and those are available in multi-viscosity ranges like 0W40 or 0w30 which make cold starts real easy. Much kinder to the engine.
Actually most marine diesels are not Yanmars, and everyone else uses glow plugs. Yanmar chose not to do so, and the cost at time of fabrication would have been miniscule, in fact Yanmar went to glow plugs after the GM series, the YM and JH series and I believe the QM series as well have glow plugs. It was a design flaw, probably due to an engineer not thinking about the fact that not all sailing is done in the tropics LOL.
The flaw is what it is, and the best way to deal with it is to treat the fuel, the tanks, and the entire system and make sure that the engine is well lubricated and maintains good compression. The Yanmar is very ticky about compression being high enough, so a slight loss in compression makes them a total pain in the arse to start when cold. Power Service additives will help this problem tremendously, and help more than you might imagine. Also the Lucas Oil additive which improves all temperature viscosity is worth using.
It is good to learn from your mistakes, but much better to learn from the mistakes of others...