Welcome to the darkside!
I took Matt's advice and skipped the CF(I blame him if I do eventually get in trouble
). i've been stopped and not a word was mentioned about the motor...they checked my catch but that was it.
I don't think you'll get 8, maybe 5-6 tops.
I get up to 4mph in my F&D...but that's a slow hull with myself(235lbs) a 70lb trolling battery(you're going to need a big one) and all my gear. I estimated my rig at 350ish lbs(plus hull weight) when loaded. That didn't include 3-4 gallons of saltwater in the bait tank @ 8.8 lbs per gallon.
I'm running a 35/36lb(I don't remember which) motor. If you can get 8 out of your 40lb I'll switch to a 40lb immediately....please let me know.