I recently connected my Lowrance HDS Gen 3 units I pulled off my previous boat and installed in a new to me Skeeter that already had a Yamaha Engine Interface already installed using a NMEA connection.

2 part question:

Should the hours displayed on my Lowrance mirror what the internal computer in the motor calculates?

Is there any possibility the hours shown on my graph would NOT reflect the exact hours on the motor? For example, would the internal computer in the motor calculate hours only based on "running" hours or could something a simple as the key being left in the "on" position despite the motor not being cranked add to the total hours?