Resistor wire location 1994 Sport Nautique

[MoKelv]

Hi everyone,

I am new to the forum, just purchased my first boat and am trying to correct some previous repairs. It appears the boat was converted to electronic ignition and is a carbureted 351W. The spark at the plugs look weak to me and are yellow in color. When I check the voltage at the coil it is 6 volts. According to the manufacturer of the coil—Flame Thrower, I am supposed to have 12 volts at the coil because there is a built in resistor. There is not an external resistor behind the motor like most of the Nautiques that I have viewed, anyone know where the resistor wire is located on my boat? I traced the + purple wire back to the connector at the motor and it checks 6 volts there as well. At the ignition switch I have 12 volts when switch is on? Anyone else encountered this same situation and know what to do?

thanks,
Bill

[Jonny Quest]

It's possible that a previous owner had a coil that required a ballast resistor. It should be fairly easy to spot as it is typically wired close to the + terminal on the coil or near the starter switch/solenoid. Since your Flame Thrower is internally resisted I doubt there is a resistor --that's why you can't seem to find it.

6V is waaaay too low. Obviously you should have 12V (switched) coming in to feed the coil. Get our your volt meter/multi meter and start by following wires. Could be a loose connection or even a bad switch.

JQ

[MoKelv]

Thanks for the reply, you have confirmed what I was thinking about the voltage being low at the coil. I don’t locate a resistor in either of the places you have mentioned. Normally when the resistor is behind the motor the metal bracket that holds it has a place to fasten to, my bracket was not made that way. The main wiring plug in for the motor on the starboard side brings 6 volts across the connection, so to me the resistor is back toward the ignition switch. I looked under the dash and didn’t see anything that resembled a resistor. I am thinking of replacing the coil to one that requires an external resistor since there is one built into this boat in some location. Any advice on what kind of coil to try? Do others have success with automotive coils on their SBF engines?