OT 12 volt question

I bought a boat that had an electrical problem. What I found was it works better if you have a 12 volt battery hooked up to the wire system. So I got 12 volts to the switches and using my tester grounded to the battery it checked out ok. As soon and I tried to use the ground thru the boat wiring nothing. So I knew it was a ground problem. After a while checking wire I pulled the lower fuse panel which someone pulled all the fuses out of. Guess what this panel was the ground. Now my question is why would they have a set of fuses on the pos wire by the switches and have the ground also on a fuse panel. I have never seen that before. This is the way the factory had it wired. I bought this boat for a tenth of the resale value so I figured I would not get hurt to bad. The motor on it is worth about 3 times of what I paid for the whole thing. I do use my tractor to move it in and out of the pole barn

If I understand your question right boats are generally fiberglass and you can,t ground to that. so you have to run both + and - to the helm from the batt.

I know you have to have a ground to the battery and on any boats you cannot ground to the hull battery only. My question is why would you have a fuse in the ground wire and the positive wire on the same circuit

you only need a fuse on one side or the other without looking at it it could be something somebody added my fuse panel in my boat has a ground section where you could add things to it, but the whole panel runs a wire back to the battery

Lots of devises for boats such as radios and GPS come with a inline fuse in both wires.
I have been told that the reason is with no ground threw the hull if one devise loses it's ground threw a bad connection it will start hunting a ground threw other devises. One large devise hunting a ground threw a smaller devises wire can cause real problems.

Typical boat wiring would have a heavy black wire from the negative post of the battery run to a central location, usually under the helm, where a majority of the electrical terminates.

The ground would connect to a terminal strip near the fuse panel. No fuse on the ground wire.

I've seen a lot of strange things on boats. Boat factories come in all sizes. Some are mega factories with teams of designers, engineers, and quality assurance personnel.

Others are one off, luxury builders, hand crafted, made to order.

Then there are the "hanging by a thread", sweat shop, minimum wage, "anything to save a dollar" shops.

So, depending on what it is and who built it, anything is possible.

Also a lot of boats are sold as bare hulls. It goes to a dealer where the engine(s) are added, steering, controls, and all the accessories are added. Again, where it goes and who is calling the shots determines how it turns out. I've seen some, especially bass boats and pontoon boats, with a lot of accessories, that were sold with some of the worst wiring ever seen!

I would look everything over closely, almost always room for improvement. Just remember, fire on a boat is an extremely dangerous thing!

That makes sense. This threw me for a loop as I had never seen 2 fuses in one circuit. The ones I worked on before had a ground bar connected to the neg post and everything else was grounded thru that bar. What I have is the top panel has 5 switches and a fuse for each under it. Then another panel seperate from the top panel with 5 fused in line under the switches. This fuses on this panel are the ground for the switch above it. It took me a while to find this out and once I did everything was working in a short order. I knew someone on here would know the reason for this setup. The boating forums did not have a clue as I found out when I asked over on them. Thanks

It would have to be an old and oddball small boat to not be 12V. Although there are still Great Lakes Freighters with 36V lighting systems.

(quoted from post at 18:32:34 09/27/17) That makes sense. This threw me for a loop as I had never seen 2 fuses in one circuit. The ones I worked on before had a ground bar connected to the neg post and everything else was grounded thru that bar. What I have is the top panel has 5 switches and a fuse for each under it. Then another panel seperate from the top panel with 5 fused in line under the switches. This fuses on this panel are the ground for the switch above it. It took me a while to find this out and once I did everything was working in a short order. I knew someone on here would know the reason for this setup. The boating forums did not have a clue as I found out when I asked over on them. Thanks

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is it possible that in order to save copper they wired it in a ring circuit?

Similar to what John said, the second fuse may be there to protect the instrument wiring from an open ground cable between the battery and motor. Generally there are separate cables for the engine and the fuse block. But the grounds may be interconnected via instrument wiring. Disconnect the negative cable to the motor, hit the starter switch and something is going to blow.