Mercury Mariner 4, 5, and 6HP 4-Stroke Factory Service Manual, Page 54Get this manual
IGNITION SYSTEM
ESURFACE INSULATION TESTOPTIONAL
CAUTION
Complete this test as rapidly as possible, as it is severe test on the coil
1Remove large red test lead from high tension spark plug lead2Plug insulation test probe into "Probe Test" jack on analyzer3Set analyzer to position 1"Coil Power Test 4Turn "Hi-Lo" current control knob to "Hi" position but DO NOT exceed meter range (4 amps)IMPORTANT: DO NOT allow test probe to linger too long at any one point5Pass insulation test probe over insulating surfaces of the ignition coil and high tension leads6If coil or high tension lead insulation is cracked, leaking or damaged, steady spark discharge will occur between the cracked or leaking surface and the test probe
NOTE: faint spark does not indicate damaged coil7Turn current control knob fully counterclockwise and put selector switch in "off" position8Replace ignition coil and leads if any surface is damaged