Looking for advice (possible ignition issue)

[Wisakedjack]

So, I went back to the boat today and rechecked voltages as was suggested. I got the following readings:

battery voltage: 12.2 V
coil '+' terminal: 11.3 V and 9.3 V while cranking

I also got the battery tester that Hanley suggested and the battery was good(!). I then fully charged the batteries and my readings got better (I did wait about 20 min after charging was complete):

battery voltage: 12.8 V
coil '+' terminal: 11.9 V and 9.9 V while cranking

But I still have the same problem. The spark from the coil lead is still weak. I see some when I hold it really close to the cylinder head (probably less than 1/8").

So, I think the battery is good and can be ruled out. Wires were replaced by the previous owner about 3 years ago. That leaves coil and EI module as possible suspects. Right? What shall I try to test next? Any advise would be greatly appreciated.

[hanleyclifford]

If you are delivering 9.9 Volts to coil + while cranking and are only seeing a weak yellow spark then the coil has to be the next suspect. If you are unsure of the coils you have in inventory maybe this is a good time to acquire one of the coils from the Moyer catalogue. Protect it with that resistor and run a bypass from the "R" terminal on your late starter.

[Wisakedjack]

Thanks Hanley for advise. I should get my new coil today or tomorrow and will report whether that fixes my issue. I went through the epic ('War and Piece' like) thread on the coils and I have one more question. There was a post linking Petronix wiring diagram on whether to connect EI module before or after the ballast resistor. Few replies indicated that people still prefer to connect EI red wire to coil '+' terminal after(!) the ballast. Is there some consensus now on what is the best practice in this regard? Thanks.

[hanleyclifford]

Thanks Hanley for advise. I should get my new coil today or tomorrow and will report whether that fixes my issue. I went through the epic ('War and Piece' like) thread on the coils and I have one more question. There was a post linking Petronix wiring diagram on whether to connect EI module before or after the ballast resistor. Few replies indicated that people still prefer to connect EI red wire to coil '+' terminal after(!) the ballast. Is there some consensus now on what is the best practice in this regard? Thanks.

I'm not real good at consensus but IMO the resistor should be connected before coil+. It is the coil that needs to be protected from excessive voltage (and amperage); the EI is only a switch. You are a good soldier for wading thru that "coilmire". After installation check voltage at coil+ to be sure it is less than 12 volts. Fair winds and tide for a cool coil.

[Wisakedjack]

Hanley, thanks for the advise. Makes sense to me.

[Wisakedjack]

Hanley your suggestion was right on the money. I put a new coil in today and got a good strong spark right away. The engine started right away without needing starter fluid (which I had to use most of the time last season). Many thanks again for everyone's help.

I still need to add ballast resistor and run a wire from 'R' terminal on the starter to '+' coil terminal. I was looking at the starter today and was not sure which one is the terminal 'R'. I am attaching a picture.



Obviously the big terminal is for battery '+' connection. White wire on the right/bottom of the picture is coming from the ignition switch. Which leaves terminal on the upper left section of the starter. Is this terminal 'R'?

[hanleyclifford]

In your picture the "R" terminal is the one with the blue insulator. But there is already a wire there - where does it go now? Maybe the system was or is wired for the bypass. If that wire with the blue insulator goes to coil+ then you are already set. Don't run too much without that resistor and confirm voltage at coil+ once it is installed.

[Wisakedjack]

Thank you for confirming. That wire blue insulation connects 'R' terminal with 'Start Isolation' terminal on the charging relay. So, its basically tells the relay that the starter is cranking. New resistor is on the way. The old one was measuring 2.5Ohm, which is way too much. I am launching the boat this weekend, so I only need to motor to my mooring

[hanleyclifford]

Thank you for confirming. That wire blue insulation connects 'R' terminal with 'Start Isolation' terminal on the charging relay. So, its basically tells the relay that the starter is cranking. New resistor is on the way. The old one was measuring 2.5Ohm, which is way too much. I am launching the boat this weekend, so I only need to motor to my mooring

Understood, but I'm curious - what does the relay do regarding the ignition circuit? 2.5 ohm does sound a bit high - I think mine is around 2.0 - but every boat is a little different and the important thing is voltage at coil +, hot and running with system at equilibrium. My view is that number should not exceed 12 volts, but there are other views out there and it is for you to decide.

[Wisakedjack]

Here is what Blue Systems charging relay manual says about 'Start Isolation':

Start Isolation allows temporary isolation of House loads from Engine circuit during engine cranking to protect sensitive electronics from sags and spikes.

Its an optional feature.

I am planing to play with the couple of resistors to find optimal mode, but in general I agree that coil voltage should be less than 12V.

[hanleyclifford]

Here is what Blue Systems charging relay manual says about 'Start Isolation':

Start Isolation allows temporary isolation of House loads from Engine circuit during engine cranking to protect sensitive electronics from sags and spikes.

Its an optional feature.

I am planing to play with the couple of resistors to find optimal mode, but in general I agree that coil voltage should be less than 12V.

I think I understand. The isolation relay, when energized by the "R" terminal shuts off sensitive electronics until the engine is running - is that correct?

[Wisakedjack]

My guess is that the relay disables charging when starting engine to avoid voltage spikes in the system.

[romantic comedy]

I took these coils off the two "spare" engine I have acquired.

[romantic comedy]

this coil I had for 25 years, just sitting around. It was in a clear plastic pack, and never used.

The word passed down to me was that you ran a resistor with a coil in a 12 volt system. With 6 volts you did not use a resistor.

[hanleyclifford]

My guess is that the relay disables charging when starting engine to avoid voltage spikes in the system.

When cranking the voltage typically drops to around 10 volts while delivering 130 amps to the starter. But I suppose the low voltage could cause the regulator to energize the field real strong and cause the alternator to spike voltage just at start up. But if the alternator is charging the battery that just started the engine that should not happen.