I get my engine hours from the Volvo display. Not sure of the specific sequence but I think it is something like:
Back out of “My View” using the “return arrow” button, use right arrow move to “Engine” display and select. The engine hours should be displayed on that page with a clock and engine icon with an “h” symbol for “hours”. When done use the back/return button to return to the main screen and select “My View”.
I have a 7212 and have not added the engine hours to the Garmin display but I know it is possible to add additional Volvo engine info to only some of the views. My recollection is that you need to to choose a view that has data bars on the right (or left?). I think you just hold your finger on the data bar item you want to change and then it will let you change that item to another one you want. I would think engine hours is available.
Hope this helps.
Curt