What is the good heat range spark plug for marine blower engine on 91 octane 120-140 engine temp.

Thanks for help.

Ac plugs mr41t

That is what I am going to run in my Supercharged engines as well. I have a 142 Thermostat in mine so the engine temps should be comparable as well.

Give me a little more info on the engine. What is the compression, boost, what heads, etc.
Eddie

I'm running a 572 Merlin, Edlebrock Aluminum Heads, 6 lbs boost, 871 blower, dual 850 Holleys, 8.5 compression, Lighting Headers, MSD. Curently using NGK R5672A-8, are these the right plugs? Thanks

The engine is 454 gen 6 .060'' overbore,B&M 250 blower, Edelbrock Performer rpm aluminum ported head, hyd roller camshaft, comp ratio is 8:1, JE flat top piston, .039'' thick head gasket .008'' deck height, twin QFT 850 carb with pv boost ref, boost for now is 5lb but i would like to go at 7-8lb of boost, timing is set at 32 deg full in at 4000 rpm for now, I will control the timing with a map sensor probaly next week, I would like to see 34-35 in cruise no boost and 30-31 at 7-8 lb boost.

Thanks for your help

I will try ngk # 8 heat range non projected plug and will see if it look too hot or too cold...

I run a B/M 250 with super chiller on a 540 with a single 1050 Dominator,I have the timing locked out at 28. I have had Zero problems with this setup. Engine starts easily and idles smooth. Boost is 6-6 1/2 lbs from 4000-5400 rpm. Carb is also boost referenced at the metering block. Its a simple setup with no worries,I do run 94 octaine fuel that is available here in Canada. I am useing Bosch HR 9 spark plugs gapped at .035. Plugs are spot on for heat range. Not an extended tip. Compression ratio of 8.1 with steel heads.