Those look like Kato Island davits, which have a safe working static load of 300 lbs (total). The 9.9 outboard weighs close to 100 lbs, and your dinghy almost certainly under 50, so you should be good. And with an outboard of that weight, I would leave it attached to the dinghy. Just be aware that in big seas the dynamic load can go way up if the boat bangs around.
Kato Marine
I'm wondering why the 9.9 on the dinghy just like Rich. People use that motor to drive 27' sailboats (I did on my previous Catalina 27) and RIBs. I'm sure other folks have other thoughts there, but in my (admittedly narrow) use case of Chesapeake Bay sailing we use 2-6hp motors in our dinghies for the most part, for short trips to shore. I suppose if you were in the Caribbean and making longer trips in bigger water you might want a honker of an outboard to plane with. YMMV.
EDIT: Our posts crossed in the ether - I see why you want the larger outboard.
Edit 2: In looking again at the Island Davits page on Kato Marine I notice it says: "
- Safe load 300lbs. (136kg) each davit arm.
That would seem to indicate a total weight of 600 lbs is safe, though the line is oddly punctuated. I own those davits, and I have had big friends use them as swing bars to enter the water off the stern (until I gently advised that isn't the purpose of the davits, thank you). While 250lb guys swung just fine off of them, they did give a little, so while I would buy 300lbs as "safe", with a margin for dynamic loads, I'd never put 600 lbs on them. I can't imagine the mounts not giving way or at least severely flexing. I think for your purposes you're well within the design limits.
