TOPIC: Airguide Synchronism Indicator

I picked up an Airguide Synchronism Indicator in preparation for my boat restoration as I intend to mount twin outboards.



Not exactly sure how this instrument is meant to be installed as it has four wires coming out.



I'm assuming one to each outboard (port & starboard), to be attached to a plug wire or similar wire receiving the pulse, one hot wire, and one negative ground.

I would guess they attach to the tachometer leads from each engine...

Exactly, green for one, red for the other? Blue power for light and white ground?

I JUST installed a NOS unit identical to yours on my 1961 Power Cat 18DC. You should have 5 wires to connect. EDIT - mine has 5. I believe you have a common ground (white) that handles the instrument light and the magneto ground. So the blue goes to light, white to a common ground for both engines, and then you need to figure out which wire goes to the kill side magneto terminal for each motor. Wire one and start the motor. If you get a signal in the wrong direction, swap to the other switch and then wire the second switch. Very easy. This assuming you're not using Mercury Thunderbolt ignition systems.

Brian