Coil check with timing light? 1977 140 HP

[kaslumber]

How is this done? I have an inductive pick-up timing light, and the motor is mounted so I could check at the lake under load if necessary. I could also use help in making the spark checking tool. I know I have seen it on here, but, now I can't find. I think I have a dead coil. I show it requires a part # 581610 or 581819. Could I replace all 4 coils with part # 582508? These seem to be more redily available?

Thanks,
Keith

 

[66 joe]

Re: Coil check with timing light? 1977 140 HP

the light helped me locate bad connection on coil on my 112 spl.
3 cyl had good light then #3 had no light. thought it was spark plug wire , but it was wire from powerpack to coil. The light flashed on both wires also once fixed, very helpful.

 

[kaslumber]

Re: Coil check with timing light? 1977 140 HP

Did you hook up inductive PU to spark plug wire and to the input wire to the coil?

 

[66 joe]

Re: Coil check with timing light? 1977 140 HP

sorry didnt answer question,,, my timing light, 2 alligator clips, 1 for +power (attached to starter solenoid or + on batt) and 1 for ground or - of batt.
Then the clamp surrounds spark plug wire for test. I also got light on small wire leadiing to coil.

 

[kaslumber]

Re: Coil check with timing light? 1977 140 HP

Does the light flash if the coil is good? And not flash if it is bad?

 

[ezeke]

Re: Coil check with timing light? 1977 140 HP

The light should flash steadily through the whole range of RPM, increasing frequency as the RPM increases. Ignition coils can work when cool and fail as they heat up. The temperature under the cowl can reach 200 degrees.

 

[jay_merrill]

Re: Coil check with timing light? 1977 140 HP

The light requires 12VDC power to work. The alligator clips go to your battery. Hook the sensor to your plug wires, one at a time. Turn the engine off each time you move the sensor from one wire to the next. Either bring a friend with you to hold the light, or place it on the deck facing the steering position, so that you can look back at it periodically, as you drive the boat.

As Ezeke said, you should see a constant and even flickering of the light. If you see no light, or an erratic flashing of it, you have problems with the cylinder involved.