My boat has electrical problems. A Quick and Dirty request for counsel!

I am posting from my cell so forgive the errors and redundancy ....

Now they might all be related or not, I simply do not know but a few weeks ago (or more) I discovered that when the aerator was turned on, it would sometimes short out or do something where the fishfinders would turn off and the one quit altogether. The new Humminbird apparently shorted or received a power-surge and it had to have the circuit board replaced. I now have a 3 AMP ATC in-line fuse between it and the power supply. I believe both fishfinders (I replaced both that came with the boat) are connected to a power source under the console. I got the Humminbird back, installed the new in-line fuses and would only turn on the livewell/aerator AFTER I had turned off the fishfinders, so this hadn’t been an issue and the aerator/livewell seems to work now…

That was the first experience.

Then, and maybe even before this all went down, I noticed the one fishfinder and maybe both would turn off – sometimes when I was simply fishing and using the trolling motor but more often when I was under power. What made this more interesting is that you could not simply power either of them back on and repeated attempts would not turn them on until they simply would turn on when I tried it again; sometimes many minutes later.

Now, in the last several outings I have seen the fishfinders quit and would not power back on for some time. I had placed a fuse holder with a 3AMP fuse (Mini ATC) between both (new, replacements) fishfinders and the power source – they are wired to something in the console where the original fishfinders were located. I had chalked it up to maybe the aerator issue but am now not sure as it had occurred allot during the times I was running the motor but now it also happens when I am not and am simply fishing. I thought it might have been a vibration issue but am not sure. And what blows my mind is how they will not simply turn back on but will (usually) some time later. I do notice this happens more when the motor is running or when I am traveling on the water this way...

There are two batteries (with a Cabela's on-board two-bank charger) where one is for the engine and the other is for the trolling motor. There are a number of fuses located in the battery compartment and then a couple under the console. Some are the glass (old) automobile type fuses and others are the plug in type (ATC, regular and mini).

On July Fourth, I went out and before I left I checked to MAKE SURE that the trolling motor was working and so were the fishfinders. However, as soon as I arrived at the first spot, the trolling motor would not turn on at all. I checked the wiring and while the plug looked like it had some residue on the interior electrical connectors, that didn't appear to be the issue. I then unwrapped the tape from around the trolling motor cable that is connected to the wired cable plug and it appeared that the one connector had come loose so I jammed it back in – they were not soldered together but had the wire ends tinned (soldered) and connected together with a crimp-style connector. However, then the glass fuse kept blowing, instantly I might add, and I ran out of fuses that fit. Now I still had issues where the fishfinders would turn off and then wouldn’t simply turn back on. Maybe a separate issue but I have to conjecture they are related.

I know have to redo the connection of the wiring cable that goes directly (with an in-line fuse) from the battery to the front of the boat at the cable plug in but I also noticed last night that the boat light on the side of the console would not turn on. And, I discovered that the bulb in the rear running light had burned up or shorted (the filament was gone) – just as I was heading back after sunset with DNR CPO's everywhere!

Luckily, no one stopped me as I was wearing a LED headlamp and had a LED Maglight pointed at the rear of the boat to show I had the light pole in but that it wasn't working...

So, I have to wonder if some of the wiring is bad, has shorts in it, there are bad connections somewhere, or whatever??? Maybe the lights are related and then maybe not…

I do not have a wiring diagram for the boat and it looks like much of the wiring added AFTER it was made is of different levels of quality. There is no fuse block that I am aware of and the fuses seem to be placed there for the following:

Protect the fishfinders
Protect the on-board battery charger
Possibly for the bilge pump
Possibly for the aerator
Whatever

I have two glass in-line fuses under the console and the two new ATC in-line fuses for the fishfinders there too. In the battery compartment there are at least six fuses (I will check tonight to make sure) and as previously stated they are there for the charger, front trolling motor, and possibly for the aerator and bilge, and maybe even for the fishfinders? There is a fuel gauge, and the boat has power trim which has not been affected. I checked the battery connections on the deep-cycle battery to ensure a good contact and even replaced it with a newer battery as this one seems have had issues charging but is under warranty. I know from experience that when I disconnected that battery the fishfinders stayed on so the electronics must be connected to the starting battery. As for the boat running plug-in lights for the stern and transom, I am guessing they too are connected to the starter battery but not sure. As for the console accessory light (switched) it was working last night so I am up in the air about why it wouldn’t turn on Monday evening.

I have not messed with the other battery and both batteries seem to charge fast. I even checked them with a voltmeter and saw they were both at optimum levels of over 12 volts each after being charged.

My thoughts are that the cable for the trolling motor needs to be fixed, maybe soldered instead of a crimp connection, and replace the glass in-line fuses (it had a 250 VOLT, BUSS AGC 7-1/2 in it) with maybe ATC’s but I am not sure what type of fuse to use or at what level. Another boater asked if I used a 50 AMP and I wonder if that is the appropriate type – it is for a Minn-Kota foot-pedal controlled 40-pounder troller. The Humminbird fishfinders are a 565 and a 161 both are basically new. The boat is a 1988 Sea Nymph Sidewinder 175 with 75HP Mercury.

Everyone’s thoughts, ideas, questions and suggestions are deeply appreciated. I would like to try and fix this myself and hope someone out there has had similar experiences and can shed some light on my dilemma(s)! Thank you all in advance!