Unfortunate no one ever converted one of these beauties. Probably fairly fuel efficient at just below hull speed.
I don't know how efficient they were. They were very heavy with really stout timbers and planking. In the later 1940s when most of them were built, fuel efficiency was not the big deal it's become today. They used the 6-71 because they were in ready supply as inexpensive surplus engines (albeit new) from the Navy, which had a huge presence in Hawaii at the time.
For their size, weight and relatively low power the aku boats were surprisingly fast, at least when empty. We were occasionally passed by one when we were out fishing miles off the north shore of Oahu or out in the Molokai Channel in my friend's 28' Uniflite sportfisherman. They would come slicing through the water at a pretty good clip. I assume part of the reason for this ability was their quite narrow beam for the length of the boat.
Since the boats were day boats there were minimal crew accommodations. There was a crude galley of sorts under the pilothouse and a few places where people could lie down.
The entire aft half of the boat was taken up with open holds, some for the live bait they netted in Pearl Harbor and the rest for the tuna that came aboard.
The elevated pilothouse served two visibility purposes. One was to see over the bow and the surrounding swells, the other was to make it easier to spot the seabirds that the fishermen used to find the fish. These were not gulls--- there are no seagulls in Hawaii, the soundtrack of the original
Hawaii Five-0 notwithstanding-- but open-ocean seabirds such as terns, boobies, frigatebirds, tropicbirds, etc. They all had Hawaiian names, but the sportfishermen called them by the types of fish they tended to indicate. So there were "aku birds" and "mahi mahi birds," and so forth.
After three or more decades of service, these boats with their wooden holds smelled very strongly of fish, a smell I imagine could only have been eliminated by replacing the wood itself.