Spark Plugs

I have used Champion plugs for years. No issues. Boats get so little use the standard copper plugs will last several seasons and at $2. per plug it is cheap.
I like the iridiums and know all the benefits but for the most part the big benefit is a little hotter spark and very long life, 200K miles.   Unless your boat is in a ski club it will never see that type work.   Standard copper plugs spark at low voltage well which is a benefit in boats. They just don't last long. Maybe 10,000 miles as opposed to Platinums which take a lot of electricity to spark and are good for 100,000 miles or Iridiums and 200,000 miles.   10,000 miles is probably what? 150 hours use in a boat?
At 150 hours you should be checking the plugs to see how it is running, good time for new $2.00 plugs. Each engine usually has the plug type needed on the valve cover plate. ( At least the older ones do ) Any plug number can be interchanged.
Champion actually makes plugs, in the Champion brand and they make them for several other manufacturers, Motorcraft and AC Delco included so I trust them.
If you work in Salt water they do offer a Stainless body spark plug for more money and sell it as a Marine Plug. Same spark but better life in salt weather when others rust.

If your engine is one of the new systems with high voltage the plugs will wear faster.
When they wear the gap gets larger. You can re gap and keep running them as long as the electrode does not get thin. Platinum and Iridium plugs use the precious metal to keep the plug from wearing and the gap does not increase with time.

Can anyone recommend the best spark plugs for a 79 Nautique-- 351 commander. I have upgraded the EI with a new dizzy, external resistor.. Is 0.035 gap ok ? thanks-- best spark plugs