Ruredy, Thanks but I was referring to how far a gap the spark would jump not the spark plug gap of .30". Sorry if I wasn't clear.
On a Yamaha Outboad the spark should jump ~9-10mm.
These Robins engines seem to only jump ~5mm
I have a home made tool but here is a link to a commercial version.
http://search.cartserver.com/search/...l=AND&go=GO%21