This is one of the simple Universal panels with only a temp gauge and ammeter. They also make them with a tach, oil pressure, water temp & volt gauge. This one has been re-terminated and has been upgraded to a new temp gauge, Teleflex Amega Series, and volt gauge which replaced the ammeter. I installed a Teleflex Amega Series gauge for the volts as well.
As you can see the key switch energizes the glow plug button first. There is then a "series jumper" that ensures the glow plug button is pressed in order to energize the start button. Personally I usually leave this series jumper in place as I have found owners will usually try to bypass the glow and not do it if they think they can get away with it. If you don't use glow, and the motor does not start, you are that much closer to filling your cylinders with water if the seacock was open.
If you feel brave and want to make the start button independent of the glow button simply move the jumper to the incoming side of the glow button, far right side, or jump to the outlet/on side of the key switch, far left. I don't advise this and do not even do this on my own vessel as I know I will try and take a short cut some day and it may cost me.
The yellow wire with red trace is the starter solenoid wire that energizes the starter. It is a tad undersized from the factory so with any resistance in the circuit, from trailer connectors or the in-line fuse holder, this can cause solenoid engagement issues. Once the trailer connectors have been removed, the wire re-terminated and new fuse holder inserted these problems often vanish even with the yellow/red wire.
As I mentioned there is an in-line fuse in the yellow/red wire close to the solenoid. This fuse holder is famous for disintegrating and ideally should be replaced when you do this upgrade. If you want to, feel free to run a new wire from the start button to the solenoid, 12GA is sufficient, and add a new in-line fuse holder.
It should be mentioned that the starter solenoid circuit is a low amp circuit. At max they pull about 2.3A +/- as measured on the "in-rush" or "peak current draw" for the circuit when hitting the starter button and capturing the in-rush with a Fluke DC clamp on DVM.. While the yellow wire can certainly handle the amp load for the circuit it is often the fuse holder or terminations that create enough resistance to cause even a low amp circuit like this some issues.
With some Universal engines I have seen the solenoid circuit wired with 14GA wire and some early ones with 16GA wire. The 16GA wire over a 20' round trip circuit, 10 feet one way, has about 1.6% voltage drop and the 14GA wire is about 1% voltage drop. If we extend the circuit to 20 feet one way, or 40' round trip we are at 3.2% voltage drop on 16GA wire and 2% voltage drop on 14GA wire. These are not bad voltage drop numbers but it you have the ability to re-use one of the other larger wires for this circuit, or run a new one, it will make your solenoid voltage drops even less.
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