as an update. It all worked "fine" The van was able to pull the boat out of the water (main concern) and returned safely to the owner's driveway where it will reside until he can find a truck.
I was at a spot in Ragland and since help would be available should it be needed my friend towed the boat out that way and launched it there. Surprisingly the van did not struggle at all pulling the boat out of the water. It ran around 3k rpms while towing and dropped from around 27 mpg to 12, however.
Thanks for all the advise and resources.