The 3 cylinder model Mercury 90, uses a NGK BUHW-2, or Champion L78V. The 6 cylinder model, takes a NGK BUHW, or a Champion L76V.
ngk buhw2 or ngk buhw
funny this should pop up i just read about this, it will run with the buhw but they don't fire as hot as the buhw-2 due to a shorter distance for spark to jump, this could lead to premature fouling. if your engine calls for the buhw-2, i would stick with them
what is gap setting for NGK BPMR7A spark plug
Your but
This plug is the Champion RCJ7Y.
The recommended spark plug for the 1977 model, 7.5 hp Mercury outboard is a Champion L78V, or NGK BUHW-2. Both brands are Perma Gap type plugs, with the Champion being the manufacturer supplied plug back in 1977.
ngk Bm6a its the same plug
cross reference ngk BP4HS
rn9y
bp4 ngk
Ngk b2lm