Am I testing my coils correctly?

[Muddyjeep810]

Edit: I have a 1977 Johnson 70 horse. When I had it running on muffs in the garage earlier the engine bogged on every cylinder when I pulled the plug wire. That tells me the engine was firing on all three cylinders.

I was just checking my coils with a multimeter. I set my multimeter to the 20 ohms range to check the primary's. From what I understand the primary is the circuit formed by the two wires coming out of the coil. One goes to ground and the other goes to the power pack. They all tested at 0.4 ohms, which from what I read should be 0.2-1.0 making the primary circuit good.

Next I tested the secondary or output circuit of the coil which i understand to be from the plug wire to the wire connected to the power pack. That's where I am getting some funky results. According to the specs I found these circuits should test between 200 and 400 ohms. So I sent my multimeter on the 2000 ohm range. I tested cyl #3 first and it tested at 1289 which is out of spec. I tested cyl #2 next and got no reading at all. When I test cyl #1 it's really weird because the multimeter reads a random/changing resistance and then instantly switches to no reading. I have seen as low as 600 and as high as 1800.

Am I doing something wrong with my testing? I have one end of the multimeter 'prongs' in the spark plug socket touching the wire element, and I have the other end where the non-grounded wire coming from the coil connects to the power pack (after removing the cover). Each coil has two wires. One goes to ground and the other goes to the power pack. Is it necessary to actually disconnect the wires from the power pack?

 

[Muddyjeep810]

I took all three coils off and the results are exactly the same as listed above. How is this possible? It ran and idled pretty good in the garage on muffs. I took it to the lake today and it ran like crap at low rpm but ran great at WOT.

 

[Muddyjeep810]

I just duplicated the tests with a second multimeter. So either I am doing something wrong or my boat was running great today at WOT ON ONE CYLINDER that even had an out of spec coil.

 

[mike_i]

When measuring resistance whatever your testing needs to be removed from the circuit.

 

[Muddyjeep810]

They are removed from the engine.

 

[gm280]

When testing coils (or any resistance readings), I like to have them disconnected from everything so I am only reading the primary or secondary windings and not anything else. Also, never touch the probes with your fingers when doing resistance measurements. Your fingers make a parallel connection and can make readings be off and variable. When you do the primaries, flex the lines to the coils to see if there are any breaks in the wires. Do the same with the secondary, especially the spark plug wires and plug connections. If there are any possible "iffy" issues, it will certainly show up doing that. Also, short your meter leads together and make sure you get a zero resistance reading on the meter with no jumping around problems. The leads themselves shouldn't jump around moving the leads either. If you can't get solid steady readings with the shorted leads, you may need new meter leads. JMHO!