New fuse block question

[mr300z87]

Hi all,

I mostly frequent the MerCruiser and boat restore forums here on Iboat, but now I have an electrical question. As part of my pre season prep, I want to upgrade some of my electrical wiring by installing a new 6 position fuse block up at the helm to power the new accessories that I have add to my 1989 cuddy cabin. My plan is to run the VHF radio, Stereo head unit (no Amp), GPS, possibly the nav/anc lights, and 12 ACC port from this new circuit and fuse block. I am going to run a RED #10 from the large post on the starter (It comes from the battery switch) to the helm and then and #10 BLACK from the fuse block to the engine block (ground). In total the wire length will be between 25' to 30' round trip. I have 2 questions 1 is 10 gauge large enough and 2 do I need a fuse/circuit beaker between the 12 V supply and the fuse block at the helm if so how many Amps. Right now everything is fed from the 12V source coming from the engine/boat harness to the helm. Any advice is greatly appreciated.

Mike

 

[alldodge]

My plan is to run the VHF radio, Stereo head unit (no Amp), GPS, possibly the nav/anc lights, and 12 ACC port

10 AWG will be great but for your listing a bit of over kill. Over doing it isn't a bad idea, because it gives you room to grow. The 10 gage wire would need a 50 amp breaker/fuse to protect the wire. What your going to put on it, a 12 AWG would be go enough and use a 30 AMP breaker/fuse

 

[Grandad]

I'd stick with the #10 wire for the main feed, but I'd only use a 30 amp fuse to protect it as near as practicable to the battery in the positive line. - Grandad

 

[NYBo]

I would run the leads directly to the battery switch COM terminal and the negative battery post.

 

[mr300z87]

So with some good weather here in NJ for change (it rained 10 Days so far in MAY I think :grumpy, I figured it time to get the Invader ready go in the water, which includes this upgrade. I was looking through my work shop and found 16 ft of #10 black and red marine wire so that what its going to be. Also decided to feed right from the common pole on the battery switch as NYbo suggested. ^^^. I ordered a fuse holder and will install a 30amp fuse within a couple of inches to the battery switch. Adding up the specs on my Stereo, VHF (if its on) and GPS is 19amps, I will use a 30 Amp fuse to feed the panel. Last weekend I spent some time behind the helm to devise a plan. This leads to another question, should I tie the existing ground (which I believe to be from the bullet connector on the engine) to my new circuit ground to the battery? My experience building grounding system for telecommunication rooms says yes. I look forward to getting this done as I like these king of project, Need to make a trip to the store for a coupe more connectors.

 

[Grandad]

It's typically required under NEC and CSA rules for building construction that such parallel conductors be of the same size and length such that they equally share the current that they are sized to carry. That said, you're probably comfortably oversized and paralleling will likely be a benefit in reducing voltage drop as currents increase. The only issue I think that could arise is if one of the conductors develops a poor connection and dumps an overload onto the remaining intact conductor. The difference in hazard here between a "hot spot" at a terminal from a loose connection would be heating along an entire length of the intact conductor which could pass through ignitable materials in your boat. But, I think I'd do it, especially if they're both #10's. - Grandad