How do I hook up a power receptacle that's only hot when engine runs?

[hodaphile]

I need a power outlet for a 12v ice chest. But don't want to always have a drain on the battery. I could easily wire it hot all the time and just unplug it when I shut the engine. Maybe YOU could remember that but I'm doing good to put in drain plug and untie the boat from the trailer before launch. Boat is a 20' I/O runabout.

A lead coming off the engine would be best as the ice chest is in the rear of the boat. I could run it off the key at the dash but it just means running a lot more wire. I thought about running it off the hour meter but the wire gauge used on it is pretty small. Running off the coil, tach, distributor, etc, always concerns me as more risky to possible damage. All my dash panel breakers/switches wired hot so that's not an option. Well, I guess I could wire it to the horn. Then at least I'd know the cooler was on?

 

[dubs283]

I'd install a separate accessory circuit for the cooler with proper fuse, breaker and switch that would be deenergized when the battery switch is turned off

 

[flashback]

Yea definitely need a relay triggered by the ignition...

 

[alldodge]

I'm assuming you have only one Bat

Run main feed from Bat or starter post thru a fuse to pin 30 on a standard square automotive relay

Run grounds to pin 85 on relay and the ice chest

Connect to any purple wire at the motor which would be , Alternator excite lead, electric choke, + side of coil to pin 86 on relay. Run pin 87 thru a fuse to Ice chest

Do note to look close at relay contacts, they will not be in same as shown on pic, but they do work as indicated

 

[Scott Danforth]

I would run the relay off the alternator output with a diode. That way if you have the key on listening to tunes, the cooler won't drain the battery