not sure what info I am supposed to be taking from this?
I quoted Scott06 who suggested connecting the purple wire that connects to the coil directly to battery positive for testing purposes.
Fitting the relay effectively does the same as what Scott06 suggested but does it automatically whenever the ignition is turned on, the purple wire is connected to battery positive (main cable) by the relay when I turn the ignition on. There is less of a voltage drop from battery to coil using the relay than there would be with standard wiring even if the dead man switch, ignition switch and all wiring were new because using the relay the length of wire to the coil from the battery is much shorter than running from the battery to the helm (and from the helm back to the coil) and the power for the ignition coil doesn't run through the dead man switch or ignition switch.
You more recently said you're measuring 1.3Ohms from main cable to purple wire, this will cause a voltage drop to the coil because the coil has low resistance of somewhere between 0.4 and 2 Ohms. It's possible to calculate the voltage at the coil, the wire resistance and the coil resistance form a voltage divider circuit... If the supply is 12V, wiring resistance is 1.3Ohms and coil resistance is 0.4Ohms the coil will only get 2.8V. If the supply is 12V, wire 1.3Ohms and coil 2Ohms the coil will get 7.27V. If the supply is 12V, wire 1.3Ohms and coil 1.3Ohms the coil will get 6V. A 30 Amp rated automotive relay might have coil resistance of 90 Ohms so if the supply is 12V, wire to relay 1.3 Ohms, the relay coil will get 11.8V which is still enough to switch the relay on. The relay is wired to switch power directly from the main cable to the purple wire at the coil, there is very little resistance on that connection so very little voltage drop to the the coil.
I would wire mine with a relay even if I hadn't had problems with the ignition because the other benefit is that the alternator doesn't overcharge the battery(s). The alternator voltage sense wire also connects to the purple wire, so if (say) there's only 9V at the purple wire because of some resistance in the purple wire (that's powering the coil) the alternator will see the battery as being at only 9V and will try to charge it to (say) 14.5V. When the purple wire is only powering the relay (not driving the coil directly) it will be at 11.8V not 9V, just a 0.2V drop instead of a 3V drop, so the alternator won't overcharge the battery(s). If there's a 3V drop on the alternator voltage sense wire and the alternator is supposed to charge at 14.5V it will be trying to charge to 14.5+3V = 17.5V which is overcharging the battery(s). I've been told there was a bulletin advising owners to connect the alternator voltage sense wire direct to the battery instead of to the purple wire to prevent overcharging, my relay setup kills two birds with one stone because it fixes voltage drop to the coil (without having to investigate kill switch or ignition switch issues) and fixes alternator overcharging without needing to move the alternator voltage sense wire. I'm not sure I'd want to permanently wire the alternator voltage sense wire to the battery, don't know if that would cause some parasitic drain on the battery with the engine turned off, using the relay when the ignition is turned off it also breaks the connection between the battery and alternator voltage sense wire.
