Chart - to show hours in between ships

See attached. I created a new column in I to get the data you wanted then used that data as the data for the labels. It doesn't have the lines joining the columns though

Take Crooza's idea, of using a series to display data labels from cells, but add another series which again is based on formula.

In J2 use =IF(LEN(I2)>0,G2,NA())

Add this data to the chart. Change the chart type of the lines to Not be Stacked lines but just Line with marker.
You should now have a line connecting the top of the columns. Add the data labels to that series and format labels and lines to suit

Thanks Andy Pope and Crooza for your responses. I appreciate it.