Oh no, another coil thread. More ohms???

[krazzz]

Last summer I installed an electronic ignition. Immediately I started having trouble which turned out to be an overheating coil. I ordered a new coil from Moyer and the problem when away until today. The weather was getting rough so I was running the motor a lot longer and harder than normal and after about an hour it just died on me. I am almost positive it is the coil. It was hot to the touch. I did not have my multi-meter on me so I couldn't test it but based on my experiences last summer I am 95% sure that it. How many OHM is the Moyer coil? Is there any harm going up another .5 or 1.0 OHM? Part of the problem is that my coil is still mounted to the engine block near the exhaust so I will be relocating it at this time as well.

[ndutton]

The MMI coil should measure around 4.3Ω but if it has truly experienced an overheat all bets are off. Please measure the alternator output voltage and coil + terminal input with the engine running at 1500 RPM to see if there is excessive charging voltage (sounds like a possibility). Throwing resistors at it without taking these measurements is a work-around and does not help in analyzing the real problem.

The engine does not have to run at that RPM very long, just enough to make the measurements.

[krazzz]

We have it on good authority that the Moyer Marine coil can handle up to 14.5 volts.

I haven't gone back to check that it was the coil but what else would kill a coil in less than 50 hours running time? I know having it located between the block and exhaust is a bad idea so I will be changing that but I don't think heat was the only issue. For the price of 1 Moyer coil I can get 3 at NAPA. (I do buy almost all of my parts are Moyer but the coil may be a different story.) Last time I went with the Moyer one because I thought that was the answer to my problems. I think this time around I am going to pick up two NAPA coils so I have a spare (And I can get them today rather than next week.)

I did read somewhere (maybe here, but now I can't find it) that after changing the gap on their spark plugs the coil problem when away. What Gap are you guys using. Also what plugs?

Thanks!

[hanleyclifford]

The Moyer coil is a little over 4 ohms and can take more of a (voltage) beating than the NAPA - but it is not invulnerable and with today's charging voltages ought to have a resistor in front of it, though it would require less of a resistor than the NAPA coil. If you do go with a NAPA coil make sure you have at least 1.5 ohms @ 50 watts in front of coil+. The boyz at the parts counter can look it up or I'll post a link if you like. Don't throw that Moyer coil away, however. It is very sound policy to get the coil off the block and mounted on a convenient bulkhead.

[Dave Neptune]

krazz, the additional gap you can run with the EI helps the idle and performance over the long run. However that additional gap will do nothing to influence the heating of the coil. The heating is the additional "dwell" of the EI and this is magnified with our slow turning 4 bangers so good VOLTAGE control to the coil is a must. IE most any coil does not need the amount of dwell for proper saturation of the primary, thus the heating as voltages rise.

I run 10.5 Volts to my coil when the charging system reads 14 and have done so for many years. In the 45 years my engine has had 3 coils of which I tossed the stock one when I built my own EI back in 83. I started using a resistor about 5 years ago and replaced my functioning coil again when I did so. Never had one burn out with the stock alt.

Dave Neptune

[hanleyclifford]

How Low Can You Go?

Happy motoring!

[krazzz]

Ok, so I just ran down to the boat at lunch. Started right up so the coil is the lead culprit. Checked the OHM of the coil and it was 4.0. With the key on, engine off the voltage at the coil was 12.5. With the engine idling I was unable to get a solid reading at the coil, the numbers were jumping all round (what does this mean?) I did get a reading at the alternator and that was 13.5. I ran it up to 1500 RPM and the reading was 13.67.

So... where do I go from here? I don't plan on running the engine this hard very often but it would be nice to know i could if I ever had to. I did notice the coil mount was a little loose and maybe caused it to vibrate too much???

[hanleyclifford]

If I were in your position I would put a 1 ohm 50 watt resistor in front of that Moyer coil right now. It is possible, however that the coil has suffered irreversible damage and will fail anyway - but maybe not. Buy the new NAPA coil as a spare. Continue to monitor voltages especially at cruise rpms. BTW, at cruise, voltages less than 14 volts at alt+ are a bit low these days. Move the coil off the block when convenient. Cooler is better with coils - always.

[Bratina]

.. With the engine idling I was unable to get a solid reading at the coil, the numbers were jumping all round (what does this mean?)

This is interesting - poor ground / loose connection maybe?

[Dave Neptune]

krazz, RE the voltage jumping around~are you sure you were on the POSITIVE terminal? The voltage being supplied should be steady, it is the negative side that will bounce around.

Dave Neptune

[krazzz]

krazz, RE the voltage jumping around~are you sure you were on the POSITIVE terminal? The voltage being supplied should be steady, it is the negative side that will bounce around.

Dave Neptune

Yes, I'm sure. I measured from that post with the engine off and it read 12.5. If it was on the negative post it shouldn't get any significant voltage. I have not touched anything on this setup in about a year and this is the first trouble I have had in at least 50+ trips. The big difference yesterday is that I ran the motor much longer than normal ~ 1hour and was pushing it pretty hard at about 1800 - 1900 RPM into a strong head wind with 6-10ft waves (we were getting soaked!) I usually only run about 15-20 min at 1,200 RPM. I have to admit I am a fair weather sailor and typically only go out on beautiful sunny days I don't see a repeat of this trip any time soon.

[Dave Neptune]

krazz, if you were indeed on the positive side the voltage should be steady engine running or not. If it was not steady running you have a weak connection somewhere, perhaps the key switch.

I run for 5~6 hours at 2200 regularly and have had no issues.

Perhaps you should try "hot wiring" to check next time. Just have a wire ready to check if it dies or stumbles.

Dave Neptune

[krazzz]

If it was not steady running you have a weak connection somewhere, perhaps the key switch.

Dave Neptune

You might be on to something. I did upgrade my gauges a few months ago. I had to pull the panel to do it. It is possible one of the wires has come loose since then. Good place to start.

[Administrator]

What troubleshooting have we done to confirm that the coil is the problem and if it is, what caused it to be a problem?

Bill

[krazzz]

What troubleshooting have we done to confirm that the coil is the problem and if it is, what caused it to be a problem?

Bill

Still troubleshooting. Last summer I put a new electronic ignition on it and it had a 3.0 OHM coil. It would run for 30- 45 min and then cut out and not start for an hour or two. Then I realized it was the wrong coil. I got the MMI coil and everything was good for a bout a year. Yesterday I was running the motor for about an hour and it just cut out exactly like it had last summer. Sailed back to the dock and tried again but it still wouldn't start. Went there during my lunch and it fired right up without me touching a thing. It matches the symptoms I had last summer exactly however I have not been able to rule out other causes. I did rule out fuel as everything was good there. My control panel wiring is my next stop. Unfortunately I will be traveling for business for 3 weeks and I'm not sure I will be able to make it down to the boat before I leave.