I had a 19ft I/O w/4.3L EFI
With the right prop the engine should handle pretty much anything. (5-blade stainless will do wonders!)
I've run with up to 2500lbs in the boat no problem.
You'll want the majority of the weight in the front. This worked good for me:
900 up front (sand & tube sac)
400 in ski locker
550 in front or rear bench seat (which was actually close to the mid point of the boat)
Add a few people and you're good to go!
My pylon was in the center though...