Whats the best plug or what plug should I use in a 1998 merc 525sc?

I'm using NGK BR6FS plugs in my Mercury HP525SC motors. I had problems with the factory plugs fouling. I think these NGK's are a little less than 1 heat range hotter. I was nervous going with the hotter plug. However, I have used them for about 8 years now without problems.

I'm not convinced the plugs I use are the absolute best for my application. I'd love to hear what other folks with 525SC motors have experienced.

I'm using NGK R5673-8 in my -93 525SC. I also used them in my previous 420/525SC clone (420 with B&M 174 blower) no issues whatsoever.

bl