Yamaha FX SVHO: Spark Plug Replacement 

I believe it was an 18MM socket. Be sure to check because it may be different on yours depending on the spark plug brand.

I didn’t do a gap. Others might disagree. A Yamaha mechanic friend of mine said you don’t need to gap. I’ve done this every year for 7 years and no issues - my ski flys… thanks for watching!