Instrument wiring

[Spindrift]

Hi All,

I recently managed to get hold of some original 'Airguide' instruments for my 1960 Owens Kent, which nicely match the existing compass and speedo. They are:
1. A 'Seaspeed' tachometer
2. An ammeter
3. An engine hours meter.

Items 2 &3 both have 2 wires coming out of the back (red and green, and red & black respectively) whereas the ammeter simply has two terminals on the back, which are nonetheless connected with a little tubular thingy of the sort you used to find lots of if you opened up the back of a transistor radio.

I would welcome any information on how I can connect these instruments to my engine/electrical system, please. The engine is a 1962 Kiekhaefer Merc 500, 4 cylinder.

Thank you.