Leave outboard on Dinghy while underway?

[j.g.evans]

This is too much dinghy and motor for worry free cruising. I have spent 12 years cruising the E coast and the Bahamas. Through trial and error I settled on a 15 HP outboard and a 2-3 HP outboard. (And a 10' dinghy weighing a little over 100 lbs.) I used the smaller engine 95% of the time. I like to still see shore when I anchor! I have had davits break with shock loads and preventing chaffing due to small movement while underway was a problem. The more weight the bigger the problems. Many time I have dragged the dinghy ashore for repairs. For your dinghy and motor I would rent a crane.