From blowing up a lot of non mercury engines, I'd agree with GLH on 1200 hp needs higher octane. At least for supercharged engines.

My 1075's have efi and a lot of safety to prevent detonation and such. I feel comfortable with puting 93 octane in them. Any more hp then that I feel your playing with fire.
Also merc's hp numbers are conservative and the engines make more power then stated.

Outerlimits Powertrain 1375's make 1375-1420 on pump gas 93 octane. I have 85 hours on a set with only using race gas for the first fill up for break in and knock testing calibration, other than that 93 octane all the way.

My understanding was, that the engine management would take care of this. Never heard that you needed to change plugs.

Well, how about 1350 HP @ 6700 on 87 oct !!! It CAN be done. It's all about air intake temps.

598's with Procharger M-5's. HP went way up with 93, and over 1800 with 110. There are 2 prs. this set is in a Skater.

Those are bad azz!

The new merc 1350's run on 91!

I just came.

Every one i've ever been on you haft to manually plug it.

Seems like you might be talking about spark plugs.

If so, what he meant was that there are two engine computers. You have to unplug the engine wiring harness from one computer and plug it into the other to switch between pump or race gas.

Them skater guy's get everything !!!!!!!!!!