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The 1998 model, Yamaha 250 hp outboard, requires an NGK BR9HS-10 spark plug, gapped to .039 in.
The Yamaha Pro 50 outboard requires an NGK BR8HS-10 plug, gapped to .039in.
The spark plug gap for most Yamaha outboards is around .030 - 0.035in.
The recommended spark plug for a 1992 model, 200hp Mercury 2 stroke carbureted outboard, is an NGK BU8H. This is a perma-gap type plug, so no gap setting is required.
The recommended spark plug gap (per NGK) is .039"
.35
The 1998 model, 115 hp Yamaha outboard, requires an NGK BR8HS-10 spark plug, gapped to .039 in.
you have to make ngk b8hs-10
0.6 - 0.7mm (0.024-0.028 inches)
.04 inch
gap should be 0.9mm (0.035") N.
The 2004 Viper Yamaha spark plug gap is .018. Most spark plugs will be pre-gapped by the spark plug manufacturer.