NGK Air Fuel Monitor With Adapter for marine power manifolds. Comes with everything in the pictures used for a short time to fine tune my carb. Plate goes between manifold & riser elbow. Adapter is 8"x4"x1" thick with 2-15/16" & 6-15/16" hole centers.
$150 shipped SPF . Located in socal (west covina).
NGK Spark Plugs 91101 - NGK Powerdex AFX Air Fuel Monitors - Overview - SummitRacing.com