Ignition/Starter Fuse blowing

[BenCT]

Over the past 12 months I’ve had a 15 amp fuse blow that is on the 12 gauge wire from my pull out knob for the ignition (I think it is also attached to the starter pull out as well). When investigating I noticed that the blower and compass light also are attached to this positive wire that runs back to a switch that ultimately goes to my battery. My wire for compass light isn’t hooked up to anything so this isn’t currently part of the problem. I believe that when I turned my blower on and left it on and started the boat, the fuse would go. I know the fan has a 5 amp surge and then drops right away to 2.4 amps. Not sure about the starter/ignition knobs as my engine is winterized and carb off and I didn’t want to mess with the starter. What should I do to fix this? Should I run a separate wire for the starter/ignition to the switch? See photos attached. Thanks for your help.

[Dave Neptune]

It is common for a single wire to feed the "control panel" and it's switches and gages. As you state that multiple wires are hooked to one I would suspect that the PO had trouble with the switches. The main power feed can supply power to the gages, blower, ign ETC. However each switch should only supply the indicated circuit. The "main feed " wire should be 8~10 gage and fused. From there to each circuit. Then each circuit should be fused separately for each source.
Each switch should only feed what is indicated by the labeling. It is never a good idea to stack various components on a single switch and it also inhibits trouble shooting and increases the chances of a short causing an electrical fire.

There are a few on this site with good electrical backgrounds that may be able to explain in a simpler fashion and include a schematic drawing too.

I would also check the + side of the coil for extra wires not part of the ignition circuit. Many mistakenly take power for there which is never a good idea. A tach wire and "possibly" and exciter wire for the alt is all that should be there.

Dave Neptune

[hanleyclifford]

Further to what Dave has said, you are correct in noting that the blower running during cranking is blowing the fuse. In addition to the amperage drain you should also consider the voltage drop the blower imparts to the ignition circuit. When cranking you need all the voltage the system can supply to fire the engine, usually in the 10 volt range. I'm surprised that you don't have difficult starting. The blower becomes a parasite. Put it on it's own circuit, as close as possible to the battery.

[BenCT]

Ok, that makes sense. I don’t know if I can get it on the light switch thingy that the PO used. See photo. For some reason the PO put this line on the light switch and that goes to the battery. In other words can I just run a new wire from the blower (or ignition/starter) and leave the other wire in place and attach the new wire to the light switch thingy as well.

[hanleyclifford]

DCpowerschemweb.pdf from Moyer Notice that no additional loads are imposed on the ignition except very small gauge loads.

[BenCT]

Super helpful, I’ve seen this a million times, but wasn’t ready for it yet. This shows an 8 gauge with 40 amp breaker. Mine has a 15 amp breaker and looks more like 12 gage.

[BenCT]

Here’s a follow up question. Why do you think the PO put this flip switch with various wires running through it like the ignition and gauges? I understand the purpose of the 1/2/B switch. Not sure if this was a convenience thing, easier to run here vs the breaker box.

[ndutton]

Here’s a follow up question. Why do you think the PO put this flip switch with various wires running through it like the ignition and gauges? I understand the purpose of the 1/2/B switch.

The age-old question, "Why did the PO . . . ?" The answer is it doesn't matter. It's your boat now and it should be the way you want it. Step one is to de-funkify the boat from the PO's dementia.

[Dave Neptune]

As Neil stated it's "your boat now" and your turn to correct the mistakes found and make it "safe" to operate with confidence. Wiring is pretty straight forward and simple when done one step at a time. Take your time to understand what is needed and do it with patience for learning your system. Just adding wires is like "adding water to a mud puddle to make it go away" .

Dave Neptune

[ndutton]

This thread comes immediately to mind. Ezra's project should be required reading.

[joe_db]

If I was still running my shop, I would suggest removing all that wiring and doing it over if this boat came to me.
It actually ends up being cheaper than hours of tracing and diagnostics to figure out all the stupid previous owner tricks (SPOT).
If you can see this right away, who knows what else you can't see