Anywhere from 0.040 of an inch to 0.050 of an inch will be acceptable. The gap is not that critical, the wider the gap the less chance for carbon deposit within the electrodes. The high voltage circuits does provide enough energy to generate a blue spark accross the mentioned gaps. Do not dwell on the subject. Gap both plugs the same and enjoy your Merc. Please use high quality oils and gas, little engines deserves the best. Pops D
Ngk bpz8h-n-10
The spark plug gap for a 2003 Mercury 125hp outboard motor is .040"
A Mercury outboard will run well with a plug gap of .035 - .040 in.
What is the correct spark plug gap setting for a Mercury outboard 2003 200 HP EFI
spark plug gap for a 1996 mercury 30 hp outboard motor?
What is the spark plug gap for a 9.9hp mercury outboard motor
For a 2005, Mercury 3.3 hp outboard, a NGK BPR6HS.
The correct spark plug gap for the 1982 model, 9.8 hp Mercury outboard is .040 in.
The plug gap for a 9.9hp Mercury outboard, ( all models ), is .035 - .040in.
.035
The correct spark plug for the 1991 model, 200 hp Mercury outboard, is a NGK brand, BU8H.
The 1999 model, 90 hp Mercury outboard requires an NGK BUHW-2 spark plug, standard plug wires are acceptable.