Should ECM total hours match hour meter?

[yams1504s]

Purchased 2 150 4 strokes - LF150TXR and F150TXR (manu 05', 06' models - although there are no 'model years' now) with Yamaha Gauges and Remote (not command link).

Have 2 Digital Tachometers plus a single Digital Speedometer and single Fuel Management Meter.

Recently performed 10hr service.

To get a baseline (and learn about Yamahas - Merc trained years ago) for future reference, I ran YDS (have ver 1.23a). Nice product.

However, the total hours from the ECM did not match hours on the Tach gauges. Off by 20 on both motors.

So my question - Is this normal? Or did my 'new' motors really have 20 hours on them before the Tach (hour meters) were connected?

The majority of the hours were in the 0-1000 - see below for actuals (I know it is rounded, but still did not expect the total to be off by so much)

5.Data Logger [Engine operating hours according to engine speed]
Engine speed Time[h]
- 1000 r/min 14
1000 - 2000 r/min 3.1
2000 - 3000 r/min 1.4
3000 - 4000 r/min 6.7
4000 - 5000 r/min 6.7
5000 - 6000 r/min 0.2
6000 - 7000 r/min 0
Total hours of operation 32

Also, are there unique ECM numbers (serial?). YDS showed identical for both of my engines.

Thanks much for any input.

[boats.net]

They rarely are the same hour reading between tach and ECM but 20 hour difference is a lot, it would seem the motors were run before the tach was installed. The ECM number is like a part number not a serial number.

[yams1504s]

Thank you.