See full version: Spark plugs for mercury outboard motor
Year & Model: 1941 Mercury KB-4 Rocket
Horsepower: 5.8 @ 4,000 rpm
Cylinders: 2-Alternate Firing
Bore: 2"
Stroke: 1.75"
Ignition: Eiseman Magneto
Point Gap: .020
Cooling: Water by rubber impeller
Condition: Unrestored
Retail price when new: $NA
Weight: 48 lbs.
Oil/Gas Mix: 3/4pt TCW-3
Spark Plug: Champion J-8J (Now J-8C but J-6C have been found to be a better heat range with today's fuel.) more
As a kid I owned a Mark 5 (see below) and it needed new J-8J spark plugs. One hot July day I took a 7 mile trip on my bike to our local OMC dealer (The closest place to our house to buy outboard parts) When questioned what the J-8J's were for, received a 20 minute diatribe on what (expletive, expletive, expletive) a product Mercury's (and Mr. Kiekhaefer) were. Now almost 30 years later I am friends with this same individual who, due to OMC's demise, is now a Mercury dealer. (And I don't let him forget it!)
Back in the 1970s there were only 2 Mercury outboards in the harbor near my home and the nearest dealer was 40 minutes away. At the time, regardless of the advertising to the contrary, they were miserable salt water motors and simply didn't hold up.
The Mercury Mark 5 will push my 12' Aluminum boat at 12.3mph. more