This 1995 Mariner 125HP abruptly failed to start out on the Sound a month ago. I had just cleared a lobster pot rope from the propeller and the motor was up out of the water. I was cranking it for about 10 seconds before remembering it was all the way up, but on putting it back down, it wouldn't start. Back home, there was no spark in any cylinder with vigorous cranking (using a CDI spark tester), with the black-yellow wire being disconnected. All the voltages were correct from the key switch wires to the engine. Got a Mercury DVA spark tester adapter, used with my Fluke 179 meter to check voltage readings from either switch box terminal, or from the stator wires themselves when disconnected from the switch box (number in parentheses). All voltages while vigorously cranking with good battery.
My DVA and resistance measurements of stator:
Across all 4 coils, zero.
Stator Red 28 (27), Red-White 24(24), Blue 190 (196), Blue-White 210 (222).
Resistances: B-BW, 6050 (but variable, see following), R-RW consistently 92. I took off the stator and took it into the house and measured resistance several times over a week. Sometimes the B-BW was 16000, or 47000 ohms, not 6000.
From the Mercury Manual about this stator:
coils, 150-250 V
Blue, 200-300V
Red 20-90V
B-BW 6800-7200 ohm
R-RW 90-140 ohm
So the blue voltages are slightly low, but it is cranking not running. And BW-B resistances either slightly low, or very high but out of range.
The stator is black, number 398-9710A31.
The current SB is only 4 yrs old and was hardly used in most of that 4 yrs so it is pretty new.
If the stator is all that is bad why is it still generating approximately correct voltages and why isn't there some spark?
Should I get a CDI stator part 1749710K1 or stick with OEM? CDI SB has heavier wire which is not encased in plastic, or should I stick with OEM.
Should I buy a Mercury switch box or get a CDI one? Any opinions about OEM vs CDI are welcome.
If the switch box is bad why did it get ruined so quickly?
Thank you in advance.
My DVA and resistance measurements of stator:
Across all 4 coils, zero.
Stator Red 28 (27), Red-White 24(24), Blue 190 (196), Blue-White 210 (222).
Resistances: B-BW, 6050 (but variable, see following), R-RW consistently 92. I took off the stator and took it into the house and measured resistance several times over a week. Sometimes the B-BW was 16000, or 47000 ohms, not 6000.
From the Mercury Manual about this stator:
coils, 150-250 V
Blue, 200-300V
Red 20-90V
B-BW 6800-7200 ohm
R-RW 90-140 ohm
So the blue voltages are slightly low, but it is cranking not running. And BW-B resistances either slightly low, or very high but out of range.
The stator is black, number 398-9710A31.
The current SB is only 4 yrs old and was hardly used in most of that 4 yrs so it is pretty new.
If the stator is all that is bad why is it still generating approximately correct voltages and why isn't there some spark?
Should I get a CDI stator part 1749710K1 or stick with OEM? CDI SB has heavier wire which is not encased in plastic, or should I stick with OEM.
Should I buy a Mercury switch box or get a CDI one? Any opinions about OEM vs CDI are welcome.
If the switch box is bad why did it get ruined so quickly?
Thank you in advance.
Last edited: