VHF Fuse selection

Searun1 · Mar 26, 2005

Rewiring my boat from previous owners job. I am installing a new fuse block as well and doing it right this time. Heres my question... I have a in-line fuse already in the positive lead right behind the Uniden radio. Do I put the same type of fuse in the fuse block? The in-line fuse is a 6-ampere fast blow fuse. What do I put in the fuse block? Thanks in advance for your help. SeaRun1

Sea Six · Mar 26, 2005

Re: VHF Fuse selection

If you're feeding the radio from a fuse block, why do you need an in-line fuse? The in-line is only necessary when feeding directly from an unfused power source.

Searun1 · Mar 26, 2005

Re: VHF Fuse selection

The radio came with a in-line fuse from the factory. The fuse is about 4" from the back of the radio. I do not want to run another wire back to the stern where the battery is. I want everything in the front of the boat to run through the fuse block under the helm. Every connection on the fuse block has a fuse so it will need another fuse in its line. That is where my question begins. SeaRun1

beniam · Mar 26, 2005

Re: VHF Fuse selection

Searun1 Cut off the 6 amp fuse, leaving 3 1/2 to 4 inches of wire. Connect to new piece of wire (same gauge,or one size heavier.(Suggest solder, then heatshrink tubing). Run wire extension to fuse block.Use 6 amp fast act. in fuse block. You now have protected radio, plus protected wire run. You only need one fuse in line, and your fuse block is easily accessible. Be happy,enjoy life. Batavier

18rabbit · Mar 26, 2005

Re: VHF Fuse selection

Since you are doing a rewire job, I agree with Batavier, except crimp a butt splice in there then cover with adhesive lined heat shrink. Do not use just solder. AWG 16 will handle 6amps easily. Since you will be rewiring mostly with AWG 16, use that. Fast blow fuses fry as soon as over-current is detected. Slow blow fuses kind of him-haw around for a bit so they are better suited to appliances with fluctuating current demands. Most onboard electronics will benefit from fast blow fuses. Even better are double pole circuit breakers. In addition to being able to reset, they function as on/off switches. When switched off the appliance is electrically isolated; i.e. no [+] and no [-].

Searun1 · Mar 27, 2005

Re: VHF Fuse selection

Excellent, thank you guys. Cutting off the in-line fuse that is factory installed doesn't leave much extra wire but it should be doable. Should I use fast blow fuses on everything in my fuse box then? I have nav lights, GPS, fishfinder, VHF radio, and a few extra spots on the fuse box. SeaRun1

Silvertip · Mar 27, 2005

Re: VHF Fuse selection

In-line fuses are not installed to protect wiring when connected to an unfused source. At that location in the circuit, they do no good for wiring shorts between the fuse and the power source. The radio manufacturer put that fast blow fuse where it did to protect the radio internals. It is not there to protect any wiring ahead of it. Therefore, leave that fuse where it is. Wire the 12V positive lead to the fuse block and fuse it an amp or two above the fast blow rating. Your radio internals are now protected as is the wiring between the fuse block and the fast blow.

waterone1@aol.com · Mar 27, 2005

Re: VHF Fuse selection

I agree with upinsmoke. Leave the inline fuse there. I also do not see any need or desire to have a double pole circuit breaker for a DC powered electronic device. The only place that you need a double pole breaker is for either a main breaker for your shore power, or for both hots on a 220V circuit.

Silvertip · Mar 28, 2005

Re: VHF Fuse selection

Waterone1 - you are correct and bring up a good point. Ground circuits should never be switched (manually or automatically). Yes I know its done with temp sensors and grounding type circuits in cars. But they are not switched for safety purposes as that's done on the primary side of the circuit.

Searun1 · Mar 28, 2005

Re: VHF Fuse selection

I bought 18 gauge marine grade wire for my trailer. Is that sufficient for most accesories like a GPS, fishfinder, radio, gauges, etc... SeaRun1

Silvertip · Mar 28, 2005

Re: VHF Fuse selection

That's a little light and fragile for trailer duty in my view, but you can get by with it for instruments as they are relatively low current draw devices.

Searun1 · Mar 28, 2005

Re: VHF Fuse selection

What gauge works best for trailer duty? I imagine I will have to rewire them next year so... I bought the 18 gauge because it looked similar to the gauge that was on the LED light set that I bought. Thanks for all of the help so far it is much appreciated! SeaRun1

Silvertip · Mar 28, 2005

Re: VHF Fuse selection

Flat tailer harness wire is usually 16 gauge and consists of four strands of wire tied together (white, brown, yellow, green). It is sold in bulk at most home improvement auto centers and is dirt cheap (but then everything is relative!!!). If you plan to use the 18 ga wire in your dash, make sure you use plenty of zip ties for support as that's not very stout wire. You would be wise to use 16 ga in that application as well. If you wire in a 12v receptacle for accessories, make sure thats a 12ga wire and fused accordingly.

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