I have a 2002 Mercury 115 hp, 2+2, 2 stroke outboard. After putting premium gas and iridiums in my small mowers (along with my regularly added Sea Foam) after your suggestion worked so well I thought I'd try them in my outboard since the lower 2 cylinders don't generate power at low rpms and as a result the plugs, although firing, aren't causing the cylinders to come up to the temperature required to burn off contaminants on the plug insulators.
Pulled up my NGK catalog, and somewhere around page 268 (recollecting) I got into the "IX" (Iridium) plugs section and cross referenced my OEM recommended plugs to IX. In the process I decided to go to a hotter plug too so I dropped down from 8 to 6 on the heat range. I was already using 91 octane gasoline as fuel so I didn't need to change that....engine is rated for 87 octane minimum but with 20-22* BTDC at WOT, pre-ignition could be a problem anyway so I already had that addressed.
Water testing revealed starts faster than you could operate the key switch and contrary to reports of rough idling with these engines, with the engine tilted up slightly so that any un-ignited fuel wouldn't puddle in spark plug area, idling around in the no-wake zone and all, you could have placed a full glass of water on the engine and not spilled a drop.
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Today's Featured Article - Grain Threshing in the Early 40's - by Pat Browning. The setting is rural Wisconsin, halfway between East Troy and Elkhorn, on Hodunk Road, our nation was at war, and I was 6, 7 and 8 years old. George was our "threshing neighbor." He was the one with the threshing machine, a JI Case on steel wheels, and he pulled it to our farm with a JI Case standard tractor also on steel. In those days, steel wheeled implements were common. The roads were general gravel, so the lugs cutting into them wasn't a problem. George would set up the thresher, s
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