Every davit manufacturer gives a max load for their davits, but even more critical is how they are attached to the boat. I seriously doubt that there is enough structural strength to fasten davits rated at 500# like ours to the stern deck of most production monohulls. It would probably require some structural reinforcement of the whole stern to carry that much weight if one considers the torque and the stresses of the dink being tossed around by the boat's motion.
A smaller, lighter dink will be a lot more fun and a hundred times more realistic, especially when you need to beach it or unbeach it after the tide has dropped a few feet. No way you could roll a 750# dink over on the beach to clean the bottom and I for one wouldn't enjoy laying on my back under a trailer cleaning it.
If speed and stability are what you are after, my Zodiac Mark 1 Classic with a 15hp 4 stroke will top out at about 35 knots with one aboard and just a few knots less with 2. With 4 adults and their gear it will still get up on a plane w/o any effort.
At about 225# it's OK to haul up on the beach, and isn't a huge strain on our davits, though we do not use them when sailing offshore, preferring to store it on deck forward. Unlike most out here, I do not like RIB's, preferring the lighter, larger load carrying capacity of a soft bottom with alloy floorboards, which I can roll up and stow below should I wish.
I do think you were on the mark with Zodiac. We love ours and it has held up really well in 6 years of hard, daily use in the tropics.
