Bkm is right, I just checked my plugs and I am running BR9ES'. I was running BR8's in my jet ski. The higher the number the colder the spark on NGK's. I would venture to guess that you are just fine running 93 octane, i would goto a BR9ES plug and maybe consider advancing your timing for optimal performance. Better yet call one of the site sponsors and get a resolution to your issue in a couple of minutes. I hope this helps.