Learned a little something.....

So, recently my Lowrance Mark 4 wasn't working after a summer trip to a lake, some kayak log rolling, and failing to remove said fish finder from a hatch before swamping it.

Dried it out, checked the in-line fuse, and it wouldn't fire up. Figured it was fried. Bought another used unit on EBay. Wired it up. Charged the battery and nothing, used unit didn't fire up. Changed the fuse, still a no-go. Change the battery.....nada......still .

Decided to change out the connectors before posting negative feedback for the dude selling a broken unit. Still a no go. .

Last resort, cut the inline fuse out of the circuit and replaced the connector....,bingo! BOTH unit worked. Pulled the insulation off the in-line fuse to find blackened wires. It was fried but the fuse was fine?? 

Anyways, moral to the story.....I'm not sure what it is other than to break down wiring to the basics before buying a new  fish finder. Also, in-line fuses work....I guess?

Now I have 3 units instead of 1 .




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The black might have actually been corrosion. I skip the fuse altogether, I don't think most of the batteries we use have the amps to damage a FF. Soldering connections also helps to cut down on the connections can fail.

I run a 7 amp battery, you think I can by-pass the in-line fuse altogether?


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I run the same battery and have never had an issue. Hopefully one of the electrical engineer types will chime in with the science of the why or why not. I think it had to do with the fact that the FF is the only device on the circuit, or something....

I would never eliminate / bypass or oversize the fuse.  First and foremost it protects the wiring / conductors from exceeding the current "amps"they are rated to carry.   I believe the power wires on my Eagle transducer cables are 18 awg.  Even a 4Ah  12 volt battery can bring 18 awg wires to the point the insulation will be melting if the wires are damaged creating a direct short.   

The fuse can sometimes also help protect the device.  A fuse rated perhaps 50% over the devices rated maximum current draw will blow should a component in the FF fail with minor damage needing to be repaired.   With a much larger fuse,  the failed component in the FF may try and draw enough current that parts are melting.   

 

So if a component in the FF fails and draws too much juice, the FF is already toast anyway, correct? So what's the point in protecting some thing that is already broken?

So you should run a fuse to protect the FF from itself?

A fuse costs under a buck.  A fish finder costs a lot more.  I've blown fuses on various occasions, which is no big deal.  If I had instead blown up my fish finder each time, I would have quit using fish finders years ago.

It sounds like your problems started when you rolled your kayak and got some part of the system wet, perhaps the fuse holder.  You might be able to prevent this problem from happening again by putting your battery system in a waterproof box.  Here are a couple of pictures of the waterproof box system I assembled, using an inexpensive waterproof box I bought at an outdoor store.  I decided to connect the battery box to the rest of the system using banana plugs, as they should resist the ravages of water and sand pretty well.  In case I manage to tear a banana plug off the end of a wire, I keep a pair of spare male plugs with screw-on connections in the waterproof box.  Someday those spare connectors may save a fishing trip.  I also keep a couple of spare fuses in the waterproof box.

I have used a water proofing device to store the battery while it was in the kayak some time ago. But, I remember some discussion on this site regarding the fire hazard of using a waterproof box with sealed batteries which always makes me hesitant.


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Did the fire hazard discussion involve sealed batteries or lead acid batteries?  Sealed batteries are sealed, so it doesn't matter if they are in a waterproof box.

The waterproof box keeps water off the battery connections. The fuse protects your kayak. Do you really want a hot knife loose in your yak?