Just installed a Flowscan in customers boat with a new 8.1L coupled to Hami HJ212 with 4.0T. I've heard they were thristy but didn't realize how much they like the fuel.
Check out the videos.
For comparison, The FNM HPE300 we installed in a Phantom Avenger with the 4.0T showed only 5.5gph at 2900rpm. 10.5gph@3400 and 17gph at 3800.
At idle the 8.1 was consuming 3gph. a 300hp diesel comsumes less the .5gph The 8.1 consumes 6gph at 1500rpm.
We weighed an 8.1 fully dressed with oil recently and it weigh 1050lbs. The 300 diesel weighs only 720lb.
There's some serious savings to be had with the diesel not only in fuel but in weight.