Best Sparkplug for 1987 Merc 470?

[ntheyer]

The Merc service manual calls for either Champ RV9YC or AC R42TS. Any better than these, or which one of the two should I use?

 

[Don S]

Re: Best Sparkplug for 1987 Merc 470?

Go for the AC, NGK, Bosch, anything but Champion. They are worthless in a boat. Only boarderline in lawnmowers.

 

[ntheyer]

Re: Best Sparkplug for 1987 Merc 470?

What is the difference between a Marine sparkplug and a non marine version. i.e. AC MR42TS and R42TS? On the AC Chart it just says M stands for Marine.<br /><br />Thanks.

 

[sikpupy]

Re: Best Sparkplug for 1987 Merc 470?

Back to the top being a land lubber, I would like to know this too.