Yamaha Hour Meter

I have a Yamaha F150 mfg date of 05/08. My 09 Sea hunt has analog gauges MPH, RPM, Fuel, Volt meter. I recently added a trim meter with the expert guidance of boats.net. I also installed a Hour Meter Yamaha part number
6Y7-083504-10-00. The hour meter has three wires yellow, black and green. I hooked the yellow to the keyed on power yellow in the harness, the black to the black in the harness, and the green to the green wire in the harness. When I turn the ignition key switch on the gauge numbers 00 illuminate. It looks like it is working. I left the key switch to on for a while and didn't notice any activity on the meter. My question is does the meter start clocking when the ignition is switched on or when the engine is actually running? If when it is running will it synchronize with the engine internal time??

[boats.net]

Wired the way you wired it will read engine running time not key on time.

Hour Meter

Thanks once again.... and if we ever get another some what warm day here in VA I'll actually put it in the water and see that. Regards