W44 exchanger anode size

[S/V AMITY]

  What is the thread size for the heat exchanger brass plug that holds the zinc?

[P69]

I have a Universal Diesel and thread size on its heat exchanger annode (that's coolant heat exchanger, not oil cooler/exchanger) is 1/4 pipe thread (NPTF).  If you are talking about the coolant heat exchanger, it is marinized part; therefore, it will likely be NPTF (tapered pipe threads) not metric or British.  It could be BSP that is close to 1/4 pip thread, so watch out for thread mismatch the thread OD  and pitch are close.

https://www.hydraulicsdirect.com/Fitting-Thread-Chart-s/1934.htm

[S/V AMITY]

Thanks P69.  Will pick up some 1/4 NPT plugs & zincs this weekend.  Cheers!