Thanks for the information, the reason I was asking was that the OMC's that I work on have a better idle and low speed operation when you get rid of the surface gap plugs.
Actually the manual for my engine says it can use either surface gap BUHW or regular type BPZ8H-N-10 gapped at .040. It says to normally use the BUHW but use the gapped plug for "Improved running quality between 1800 ? 2000 RPM". My engine is of the 2+2 design. The running quality must be for the kicking in of the bottom two cylinders. I have tried both plugs and found that the acceleration is better with BUHW but you do notice bottoms kicking in and out more.
There is no conventional sparkplug specified for that motor. A conventional sparkplug will probably not hit the top of the piston, however, the heatrange will be incorrect, and it could cause damage to the motor.
As other posters said, if you have idle problems, it is not the plug's fault, but more likely dirty or misadjusted carbs.
