The ceramic on one of the plugs broke right off on the HP500 Carburated. So put in in a back up old plug and want to replace all plugs with new.

The stock plug is BR6FSThe upgrade to iridium is the BR6FIX

Any difference in performance between these plugs on a boat? or better fuel economy or durability?

I've read mixed reviews. Curious what others use and if they have the iridium any improvement?

Thanks,

NGK BR6FS and AcDelco MR43T's are good plugs. Not sure why'd you want iridium unless it makes you feel better ? If so, fine.

Check tune, usually thats a sign of detonation..

Iridium plugs will give you a better at any gap compared to standard plugs.

The micro focal point of the positive electrode will focus the energy (and minimize the voltage) required to jump a gap with a spark.

I've found them to a lot more robust, as well.

In a supercharger aspirated engine, with high cylinder pressures, a good aggressive spark is a necessary component to a healthy engine. A good initial spark kernel can stave off detonation, by a faster overall burn.

Unless you are going through plugs for some reason, I would use Iridiums. It's like saying that you don't want to use the new tech of an extended tip spark plug back in the day.