12v only when ignition on

[tgillson]

Hi all,
I've got a 1800sr3 and cannot figure out what DC is supervised/controlled by the ignition switch. All of the electrics appear to be live when the boat isn't running. I want to wire a relay to switch in a starting battery with the ignition but can't find a 12v to wire the relay coil.
Does anyone know a suitable place to get a ignition controlled 12v for this application?

Thanks

[mmwjr]

What electronics do you want to put on this relay? Seems you would want them to stay on when at anchor or drift fishing.

[tgillson]

Hi yes, basically I have all the boat + DC connected together on one lug. I've run a cable from a deep cycle to that lug for power at all times. Also connected to that lug is another battery through a solenoid.
The idea being when I'm floating.the deep cycle is running everything and when I key the ignition I'd like the solenoid to close to connect the other battery for starting purposes. While running they would both be connected and charging.
At this point I've run the solenoid coil + to a dashboard aux switch so I'll turn it on like the blower before I start. It'd be really nice to find a switched on DC from the ignition to do this automatically though.

[mmwjr]

The purple wire under the dash gets power when the key is in the run position.

[donald]

Question?
Is that for continuous use?
If not it may cause a fire also is it marine certified?
Don

[tgillson]

Hi Don,
It's rated 300amps continuous and not marine rated. I boat on lakes and it won't see anything more corrosive that the automotive environment it was intended for.
Although I may be underestimating marine conditions. I thought corrosion due to salt was the main concern and my boat doesn't see any salt.

[mmwjr]

Originally Posted by tgillson

Hi Don,
It's rated 300amps continuous and not marine rated. I boat on lakes and it won't see anything more corrosive that the automotive environment it was intended for.
Although I may be underestimating marine conditions. I thought corrosion due to salt was the main concern and my boat doesn't see any salt.

The main concern when it come to electrical items on a boat is ignition protection. Seal unit so sparks cannot escape in the presence of fumes.

[donald]

+1 with Mike, he is right on!
Don't want things that go BOOM!
Don

[tgillson]

Thanks for the replies. I understand gas vapour and the need to run the blower to avoid blowing up the boat. I don't understand the concern here though.
The solenoid contacts are in a dielectric fluid. So the only risk of sparks would be if the cables work lose and short to ground. The batteries will get a terminal buss fuses when they finally become available again.
Wouldn't the alternator and starter not the biggest source of ignition?

[mmwjr]

Originally Posted by tgillson

Thanks for the replies. I understand gas vapour and the need to run the blower to avoid blowing up the boat. I don't understand the concern here though.
The solenoid contacts are in a dielectric fluid. So the only risk of sparks would be if the cables work lose and short to ground. The batteries will get a terminal buss fuses when they finally become available again.
Wouldn't the alternator and starter not the biggest source of ignition?

I’ve never seen a soleniod filled with a dielectric. The alternator and starter have spark arrestors in a marine application.

[tgillson]

I didn't realize, thanks for the info. I'll look into the solenoid regarding any possible sparkling as well