Small boat wiring question

[mosk]

I have read the FAQ and the "generic boat wiring diagram" thread and still have a question or two about my situation: I have a small 12' aluminum Klammath fishing boat. My current electrical system consists of a 12V deep cycle battery, an electric start 15hp Nissan O/B with alternator output, a MinnKota PowerDrive trolling motor, and a Humminbird fishfinder. Currently, all of these are wired directly to the battery. They work fine, but I'm relocating the battery to the front, and as long as I'm running wires, I'd like to install a master switch and either a fusible link or some other form of circuit protection, just in case something shorts in a big way.

Unfortunately, I can't find the amperage drawn by either the trolling motor or the starter motor, so I don't know what sort of a load to plan for. Does anyone have any rule-of-thumb values to use for the connection to the gas motor and/or the trolling motor? I'd prefer to use circuit breakers on these connections, and will wire them individually to a distribution block.

In my mind, I see the system taking this sort of form:

Battery > master switch > fusible link > distribution block > three individual circuit breakers for the trolling motor, alternator/starter, and "other accessories".

Any thoughts? Does the above seem reasonable, or is it overkill?

Thanks,

Jeff

 

[Silvertip]

Re: Small boat wiring question

You do not put circuit protection in the large battery cable between the engine and the battery. You can however install a simple battery switch (a master if you will). These are simple on/off devices available at any auto store. For accessories, you need a circuit breaker for the trolling motor. 50 amp will probably be ok but it depends on the size of the trolling motor. Other accessories need fuses or breakers sized 10% higher than the total current draw on the circuit. Do not combine high and low current draw items on the same circuit. For example do not connect your fish finder to the 50A circuit breaker for the trolling motor. A problem in the fish finder circuit would not trip the 50A breaker before a fire broke out. Forget fusable links. They are expensive, difficult to replace on the water, and too slow acting. You need a breaker in that position.

 

[mosk]

Re: Small boat wiring question

Thanks for the recommendations, they are much appreciated. Any thoughts on the circuit protection (i.e., amperage) necessary for the electric starter?

-Jeff

 

[Silvertip]

Re: Small boat wiring question

Get off the protection for the electric starter. You do not fuse that circuit. There isn't one on a car, there isn't one on a truck, and there isn't one on a boat. There is a fuse in the engine but it is for the "engine" harness which includes the feed to the starter solenoid. So it is already protected.

 

[mosk]

Re: Small boat wiring question

OK, OK.

Thanks for your help. I think you've given me a good understanding of what I should (and should not) do with these circuits.

-Jeff