For a 2000 model: The Spark Plug (1) is located in the rear of the engine (opposite the pull start), beneath the gas tank. There is an access hatch. It can also be seen apon removal of the upper engine housing cover.
The spark plug gap for a 2003 Mercury 125hp outboard motor is .040"
A 50hp Mercury outboard motor typically has two spark plugs. This configuration is common for two-stroke engines, which often use one spark plug per cylinder. If you have a specific model or year in mind, it's always best to check the owner's manual for precise details.
spark plug gap for a 1996 mercury 30 hp outboard motor?
What is the spark plug gap for a 9.9hp mercury outboard motor
100 hp searay
3 spark plugs
.025 Champian J4J (cold) to J8J (plugs) Points .018 - .02
.040
NGK bpr7hs-10
The spark plugs on a 1988 model, 70hp Johnson outboard, should be gapped to .030in.
Ngk bpz8h-n-10
The recommended spark plug for the 1977 model, 7.5 hp Mercury outboard is a Champion L78V, or NGK BUHW-2. Both brands are Perma Gap type plugs, with the Champion being the manufacturer supplied plug back in 1977.