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I am doing the Turbo upgrade to Sonex 0861. The only "convenient" place to relocate my master contactor is on the engine mount with a couple of hose clamps and some Silicone tape around the motor mount. I don't know if that violates any long held conventions or not? If I mount the contactor there I can use most of my wiring from my original set up. Anyone see a problem with the master solenoid not on the firewall?

Bill,
I think if it survives the extra bit of vibes there is nothing wrong with it.

That's what I did as I've seen it on vintage planes. It works fine.
Happy Landings
John
N50NX

My only concern would be the contactor rotating around the tube due to vibration or clamp failure, and the terminals shorting out on something.
Another place to mount a master and/or start contactor is on the side and front of the fuel filler bay.
A couple of nutplates on the inside would have plenty of bolt clearance from the tank neck. Just locate them low enough so they don't interfere with a future drip tray surrounding the filler.

Thanks guys. I went ahead and placed the contactor on the engine mount, There are several wraps of silicone tape to protect the mount. the terminals are both booted and where it sits even if it spins it wont contact anything. With the heavy gauge wires I don't think it will move even if i removed the clamps. Oh well, another experiment.

I bolted mine to the battery box

I bolted mine to the battery box as well (on a side). My engine is not Turbo AeroVee though, but Revmaster 2300.

I have a question regarding the contactor being pretty hot in about 20-30 minutes after turning the master switch "on". I can briefly touch it, but cannot hold my finger on the body of the contactor. The bottom of it is hotter than the top. Is it normal? I conducted a test having it "ON" for 2 hours, it did not burn yet. Maybe it is normal, but I did not expect it to be so hot. Mine is s701-1 from B&C. I would appreciate any information about this. Thanks!

Your master contactor serves as a ~10 watt heater due to the 15ohm coil (12v system/15ohm = 0.8 amps; 0.8 amps ^2 * 15ohm = 9.6 watts).

I use an automotive relay instead of a contactor--it only draws about 0.15 amps through the coil, but it can only handle 40 amps and can't be used to completely isolate the battery from the circuit.

Hi Chris

How do you control the power that goes to your starter? Happen to have a wiring diagram?

Gordon

Thank you Chris.