I reckon we have all done it, - browsing through eBay to find the best price spark plugs for our outboard/inboard motors - I always have a preference to NGK's as they have performed well for me in the past, but there are some worrying posts on the Web concerning counterfeit NGK's that can damage engines.
Some Scary stuff below -
http://www.scc-racing.com/racing-blog/w ... park-plugs
http://www.ukantipiracy.co.uk/cars/ngk.html
http://www.slideshare.net/athangal/dist ... spark-plug