912is/915is EMS POWER

Allen Asked Elsewhere:

Regarding the start power switch and battery backup switch, is it convention to wire those as shown in the Rotax Installation manual for the 915i series?
My kit manufacturer shows relays inserted between the circuits and the switches.
I’m building a Sling TSI. 
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You can use either Relays or DPDT switches.
Switches look neater on paper but not so in real life.
Remember that the manual depicts a schematic, Not a pictorial.
A relay is just a remote controlled switch and is functionally equivalent.  The engine doesn't care!

Relays are often result in a neater installation and require less wiring than switches.
Relays can be located close to the engine and battery with much shorter wires required.
The relays can be energized by a small switch using smaller gauge wire (often a single wire) for the longer connection.
Switches will require longer heavier wires capable of carrying the full Power and Ground loads from the battery to the switch and then back to the Engine.