Yanmar coolant plugs for heater

[David Wesner]

I’m looking for information on the correct type of fittings for the heater ports on a Yanmar 6LYA-STE. The service manual calls them 3/8″ pipe threads. They are either NPT or BSP. Measured what was on the engine and it appears they are NPT as they are slightly larger than the BSP. Did someone wind them into the BSP female threads before I got the engine. What is it supposed to be? thanks

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[David Wesner]

Thanks for the info. Spoke with mack boring and they confirmed it was BSP 3/8″. Removed old plug and saw some thread smashing. I was able to fit the BSP fitting without concern. Posting for anyone else looking for the information.

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[Tony Athens]

99% sure they are 3/8: NPT

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David Wesner

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