1998 Mercury 200 HP V6
Serial #: 0G638250
I am experiencing tach issues (reading higher rpms than actual). As a result, I decided to test the rpm of each cylinder by using a timing light with an inductive tach by clamping to each spark plug wire. The #5 and #6 wires are reading upwards of 6500 rpm at idle while the other spark plug wires show roughly 1000 rpms (using the timing light with tach) all while running on the muffs at idle.
Are there any reccomended tests I can try to isolate the problem?
#5 cylinder:
20230312_151605.jpg
#2 cylinder:
20230312_151620.jpg