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SPDT Rotary Switches and SPST Relays


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As some of you may seen in a related post, I am in the planning phase of an automatic ballast installation for my 2000 23LSV. The plan is to begin the installation this weekend so time is now of the essence. It is also about 90 degrees here in Dallas so I’m dying that the boat is not ready to go. I appreciate the help!

I have completed the sidewall reinforcement portion of the project and think I have the plumbing of the 2 Johnson reversible pumps figured out (for now). I also believe I have a decent plan for relocating the battery from the port trunk to the observer compartment and the addition of a blue seas switch to the trunk. The portion of the install that I am still not comfortable with is the wiring of the switches. I bought two SPDT rotary switches that will install cleanly in the unused accessory slots on my dash for a factory look. Thanks to the help of those on this board I now understand that these switches (http://www.marineeng...php?in=1907873_) will not work on their own. I have since purchased four SPST relays and I want to confirm the wiring. I came across this diagram on another board and would appreciate you all’s opinion on whether or not this will work.


For those that sense my incompetence from my prior posts and worry about me electrocuting myself or setting my boat on fire take some comfort in the fact that my boat partner is 100x more knowledgeable about this stuff then me. Since I will be largely responsible for making sure his beer is full and cold during the actual install, I am trying to do as much of the legwork on the front end as possible. I appreciate the help!

Edited by newbie1000
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That looks like it'd work. Jut make sure your main power to the relay's fused if something goes bad. To reduce clutter you could use a double pole double throw. With a dpdt it mechanically protects you from shorting the hot to ground.

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Thanks Cowwboy. I will definitely make sure the power line is fused appropriately.

I am going to use 12 AWG wire for the “thick” runs. What size wire should I use for the “thin” runs?

Also, I am thinking I can save some money on wire by having the relays close to the pumps and blue seas switch so that the 12 AWG runs are short and the long runs to the dash are with “thin” wire. Does this make sense? Is there any reason I would want the relays under the dash?

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Personally I would tap into your main power off your alternator or starter tap. It'll be very large gauge to those an will cut your costs down. Then just use a twisted pair or 4 conductor of small gauge to fire the relays. Being that they are just signal wires and not high current you'd be fine running a smaller gauge. My best suggestion on size factoring and general electrical reference is pick up a ugly's quick guide. I don't know the IMei number but they are a great reference. I think most book stores Cary em.

Edited by cowwboy
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