Kato davits rated for 350#. I leave my 80# 9.8hp outboard (and fuel tank) attached to the RIB (92#) while underway. But Kato's are very well designed, and I included their optional rail braces. Kato also provides optional SS ratchet straps that keep the boat from racking side to side while underway. Very important when underway. It looks wild, but works well, even in a gale, heeled 20 deg. I would not recommend this for many davits out there. Take the engine off and cross-strap the dinghy to prevent racking.
RIBs tow better with engine than roll-ups do, but either one is a dicey situation that puts your engine at risk when the seas build. If you don't keep the boat on the right length painter it can get behind a wave and snap the painter under tremendous load. Get it too close and it will ride a wave into your stern. If is skids too far left/right, it will be prone to a hard whip that flips the boat. If I tow, I use a bridle that ties to the bow tow ring (thru bolted to the RIB fiberglass), and ties off on each rear cleat. That way you can keep the dinghy in your "slick", tracking like it is on rails.
RIBs tow better with engine than roll-ups do, but either one is a dicey situation that puts your engine at risk when the seas build. If you don't keep the boat on the right length painter it can get behind a wave and snap the painter under tremendous load. Get it too close and it will ride a wave into your stern. If is skids too far left/right, it will be prone to a hard whip that flips the boat. If I tow, I use a bridle that ties to the bow tow ring (thru bolted to the RIB fiberglass), and ties off on each rear cleat. That way you can keep the dinghy in your "slick", tracking like it is on rails.