1975 Mercury 500 thunderbolt 50hp 4cyl - what is spark plug #?

tunerauto · #1 June 14th, 2009, 02:17 PM

Doing the maintenance on my newly acquired boat and I want to replace the plugs. Im getting the Selco manual for it but till then I will have to ask alot of questions. I also dont have a o/b store readily available so I will have to order alot of my stuff.
Question is , what Champion or NGK spark plug number do I get for this motor?

Aqualift · #2 June 14th, 2009, 03:01 PM

AC-V40FFM or Champion L76V, OR NGK BUHW

tunerauto · #3 June 14th, 2009, 09:32 PM

Thank you , Gap?

Moody Blue · #4 June 14th, 2009, 10:20 PM

These are surface gap plugs. No bent electrode of the end of the plug, hence no gap to set. They are what they are.