Logo
FULL SITE MENU

Voltage at coil

S

stuski

New member
Hi Everyone,

I have a 28" Uniflite with twin 318's. Have question about coil voltage as I m getting different readings from one motor to the other.
Have new Mallory ignitions YLM579AV. Flame Thrower 1.5 ohm internal resistor coils. When I check voltage with ignition on at + terminal to ground port side I get around 8 volts. When I check star. side + terminal to ground I read 12.5 v. Both coils are new. Also when I check star. side coil - terminal to ground, I am reading 12.5 v. also.?? I am confused as to why. The only way I can duplicate this on the port side is to disconnect the distributor wiring plug.
Both sides read 12.5 v. from ignition switch wire when it is disconnected from coil.
Recently had a lightning strike to outrigger which fried both tachs, fuel gauge, hour meters, rudder indicator, and my underwater lights :mad:!!! Both motors ran after the lightning strike as the tachs not working were the first clue that the boat was hit while docked in the marina. Shorty thereafter we replaced the tachs, then the star. side would not start. No spark. Replaced the ignition module and now motor runs as normal.
Now I wonder why I am reading different voltages at the coils and if the lightning is what killed my module or something else like too much voltage to the ignition from the coil.
Any advice would be greatly appreciated

Thanks, Stuski
 
kimcrwbr1 said:
Did you check the resistance on both the primary and secondary windings in the ignition coils. Both coils should be real close?
Click to expand...

Yes, they are the same. Both were newly installed yesterday. The old coil on the star. side was reading only 1 ohm primary resistance before so I thought that was the problem. But I am still getting the same voltage readings as before with the new coils. I also found it strange that when the distributor leads are unplugged on the port side I get the same volt readings as the star.side whether the distributor leads are unplugged or not.

Thanks for the reply, Stuski
 
I had that problem with my old boat. Had 12 volts going to the ignition switch at the helm, but only 8 or 9 volts arriving back at the coil. Replaced all kinds of stuff (including the switch, fuse, breaker) and even ran a second wire, all to no avail. Ticked off, I installed a relay at the distributor to take a full 12 volts right off the battery cable and send it to the coil. No more problems.

Jeff

PS: Got the Bosch type relays on eBay. Cheap.
 
fastjeff said:
I had that problem with my old boat. Had 12 volts going to the ignition switch at the helm, but only 8 or 9 volts arriving back at the coil. Replaced all kinds of stuff (including the switch, fuse, breaker) and even ran a second wire, all to no avail. Ticked off, I installed a relay at the distributor to take a full 12 volts right off the battery cable and send it to the coil. No more problems.

Jeff

PS: Got the Bosch type relays on eBay. Cheap.
Click to expand...


Hi Jeff, Thanks for the reply. Crazy thing is when I test wire coming from ignition switch disconnected form the coil I read full battery voltage. When connected to the coil it reads about 9 v. I thought this was correct as the coil provides resistance. Not sure exactly how this works with the resistance in the coil but when I disconnect the distributer leads it will read 12v. on + terminal to ground.(and 12v. - terminal to ground too?). Which these are the same voltage readings I get on the starb. side with the distributor leads connected or not.
I thought with distributer connected the resistance of the coil comes into play and reduces the voltage. Perhaps I am looking at it the wrong way and the star. side is correct reading 12v. What should my readings be? I am on my way to the marina now to double check everything again for the 10th time and take more readings. Thought I would run them too and take readings while running. I just don't want burn out any modules or other parts. Also for peace and mind I think both engines readings should be identical.

Thanks again for any help Stuski
 
kimcrwbr1 said:
If these are points to electronic conversion (pertronix or hot spark) It is real important you have battery voltage or close while running at the ignition module as well. Low voltage will fry the module pretty quick.
Click to expand...

No I have new Mallory distributors I have battery voltage, 11.79 or so on the star. motor 9 v. on port. coil + terminal to ground. Port coil running 150 degrees vs. 115 degrees on star. side

See volt readings below from today.

PORT COIL STARB. COIL

+ _ terminal + - terminal


9.0v 1.6 v. to ground 11.72 v. 11.72 v. to ground

11.82 11.82 to ground W/ dist. harness disconnected. 11.79 v. 11.72 v. to ground W/ Dist. harness
disconnected

No performance issues as of yet, but have not taken for ride yet. Seems to be running normal at the dock. Wonder why I have the different readings, and the coil temp. difference. What temp. should a coil be running at?

Thanks, Stuski
 
stuski said:
No I have new Mallory distributors I have battery voltage, 11.79 or so on the star. motor 9 v. on port. coil + terminal to ground. Port coil running 150 degrees vs. 115 degrees on star. side

See volt readings below from today.

PORT COIL STARB. COIL

+ _ terminal + - terminal


9.0v 1.6 v. to ground 11.72 v. 11.72 v. to ground

11.82 11.82 to ground W/ dist. harness disconnected. 11.79 v. 11.72 v. to ground W/ Dist. harness
disconnected

No performance issues as of yet, but have not taken for ride yet. Seems to be running normal at the dock. Wonder why I have the different readings, and the coil temp. difference. What temp. should a coil be running at?

Thanks, Stuski
Click to expand...
Sorry when I sent it condensed the way I had it written to show coil v. readings.
 
Back
Top