NGK plugs.

Maybe marine buys more so they get them cheaper? Or winter sale just to move them along.
If they are genuine plugs those are very inexpensive. Boat people don’t mess around…. When on the water- you cannot walk home if you break down. I know I’ve bought “genuine Johnson” out board coils before. One went out 20mins out. Lucky I made it home on one cylinder. They were fakes- eBay. I bought 2 from the dealer and never had an issue. Thanks for the letting us know about these.