Re: Spark Plug Conversion Question
Platinum plugs would offer you no performance advantage over a standard copper core spark plug.
The reason platinum plugs exist is due to their longevity. Platinum is a harder material compared to copper, and that being said does not need to be changed as frequently. This is an advantage in an automobile which has seen its maintenance intervals extended from the big 30K service of the past (which included changing the spark plugs) to a 60-90K service where spark plugs are now typically changed. The difference between modern automobiles, and your engine is the simple fact that an old 2 stroke like yours wouldn't be too happy tolerating longer plug change intervals, especially if you use your big twin for allot of trolling. The plugs will still foul just as quickly as a coper core plug, and will cost more to replace.
It can also be argued that a copper core spark plug is more conductive, as copper in it's self is a more conductive material than platinum. Of course the use of platinum with a modern ignition system will have no detrimental effects, as most automotive ignition systems are very capable of producing 50 Kv + on their secondary side, where as your old outboard with a magneto powered ignition system on it's best day may be able to muster 10-15 Kv. What that translates to is you would potentially have the more reliable, stronger spark using a copper core plug with your ignition.
In a nutshell, leave the gun...er uhh platinums, take the copper...
