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Question About Marine Switches

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Stovebolt
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Question About Marine Switches

Post by Stovebolt » Thu Aug 25, 2011 1:58 pm

I'm just wiring lights into my little fiberglass boat. I bought a marine pull switch, but it only has 2 screw terminals on it. Aren't they supposed to be grounded? My brain won't stop thinking like I'm wiring a switch into a car, so, I just need some guidance with this.

Thanks for any info folks.
1961 Chris Craft 17' Ski Boat
1973 15.6' Hourston Glasscraft

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mfine
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Post by mfine » Thu Aug 25, 2011 3:13 pm

One side is positive and the other is ground.

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Post by Stovebolt » Thu Aug 25, 2011 3:17 pm

Wouldn't one be power in, and the other be power out? I think I cleared my head enough to figure that the switch is just a break in the wire, it doesn't need the ground?
1961 Chris Craft 17' Ski Boat
1973 15.6' Hourston Glasscraft

farupp
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Post by farupp » Thu Aug 25, 2011 3:43 pm

You are right, Stovebolt. It's just like a light switch in a house. The switch completes or interrupts the flow of electricity to the light. The light socket itself is what is grounded.

And, I think a car is the same, at least the ones I have worked on, not counting the British cars with Lucas "Prince of Darkness" wiring and electronics. :evil:

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Post by farupp » Thu Aug 25, 2011 4:11 pm

I am revising my previous post somewhat as there are some circuits that I have found on boats where the switch does complete the ground circuit and one terminal on the switch is connected to ground. The horn button and horn circuit is an example. I don't remember finding a light switch, however, that completed the ground circuit.
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1959 22-foot Sea Skiff Ranger
283 Flywheel Forward engine

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mfine
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Post by mfine » Thu Aug 25, 2011 4:24 pm

Yes, it is a simple wire interupt on DC. When the switch is open, one terminal should measure +12-14.5 volts (depending on if it is on batery or the alternator/generator and engine speed etc.) and the other should measure 0 relative to ground.

When closed, they should both read the same +12-14.5 volts to ground and 0 volts relative to each other.

What would the third wire to ground be for? To ground the body to protect you from the potential for a 12 volt "shock"? That is not really a concern, but if you are worried about it, you can ground your metal dash and all the switches will be grounded through their shafts, or alternatively gound one switch and they will all be grounded through the panel.

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mfine
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Post by mfine » Thu Aug 25, 2011 4:28 pm

farupp wrote:I am revising my previous post somewhat as there are some circuits that I have found on boats where the switch does complete the ground circuit and one terminal on the switch is connected to ground. The horn button and horn circuit is an example. I don't remember finding a light switch, however, that completed the ground circuit.
There isn't much difference where you put the switch. When open, everythng on one side is possitive and the other is at ground. Usually you put the switch nearest the possitive source so you have less "stuff" sitting at a possitive potential waiting to short on something. I think Stoves question was more about a chasis ground for the switch housing itself, outside the active circuit.

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Post by Stovebolt » Thu Aug 25, 2011 4:41 pm

Thanks you guys. You have strightened it out in my brain! :D
1961 Chris Craft 17' Ski Boat
1973 15.6' Hourston Glasscraft

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