1970 75 (7.5) merc proper spark plug ?

[roonie]

Looking for proper plug to fit this engine. Every chart i look at shows a different #. This website shows QL78V. When i speak to my in town shop, both shops say L86C...im at a loss. Can someone tell me what the proper plug is. My engine serial is #2957779 and it has thunderbolt ing. Thank you

 

[hardwater fisherman]

I looked at a few sites and they list QL78V for 1970 to 1978. With an alternate plug of L78V. And QL86C is listed for 1967 to 1969. The L86c is listed as an alternate for 1967 to 1969.

 

[roonie]

thanks.....no shop around here has that QL78V so i got him to cross over to a NGK plug....BUHW-2