I am in the process of getting my engines back together. They are 97 Gen VI 502 MPIs with the B@M 250 Supercharger kits on them. The engines just underwent a total top and bottom rebuild as well as having my superchargers re-blueprinted as well. My question is should I just run the normal merc recommended plugs or does anyone recommend a better plug with a colder heat range than the originals?

my motors r not suppercharged but i relly like the ngk's

Actually the NGKs are what I was looking at. I have heard nothing but good things about them. I am not sure exactly which NGK plug I should run though.

i have hp 500,s bm 250 intercooled 5 1/2 boost and run ac mr41ts plugs dynoed last year at750 plus never an issue,also they are now for sell,,upgraded reason for selling

sorry i meant mr43t ac plugs gapped at .027

I would run NGK R5673-8. I have been using them in blown engines for years.

I would run a plug that is 1-2 heat ranges cooler than stock

Stock plug is AC MR43T or NGK BR6FS
You can run AC MR42T or MR41T("M" is for Marine and you you can run non marine plugs without issue)
NGK cooler plugs are BR7FS and BR8FS

So for the supercharged engines you also want to decrease the gap from OEM specs as well?

I am trying to understand the science of all this. I am researching the web as well.

Griff - thanks

This is all great info for me.

You want a colder plug, to prevent pre-ignition. You also want a smaller gap so the spark doesn`t get "blownout".
Thats what I`ve always done