as i recall
this valve is a specialty part . even though it looks like a standard 1/4 nut there is a long threaded specialty brass drain fitting attached to the nut. you'll need to call a local distributor like MER marine
to look in the parts
manual and get you the correct drain for your engine
. as i recall
those drain plugs are pricey about $20 apiece . yanmar
HQ in ILL now refers all tech questions to your east coast or west coast distributor which is MACK BORING on the east coast. you might also try calling mack boring as their parts
guys are superb..
by the way those 2GM
mixing elbows have a reverse thread on them. one end is lefty loose and one side is righty loose.