I ran one on my 82 115hp merc. for 15yrs no issues with stress or strain on the boat or motor. When I traded up to a 95 150hp Johnson I put one on that boat as well and ran it for 17yrs with no issues with stress or strain on the boat or motor.
Cons, you lose one or two mph top end.
Pros, 1 boat planes guicker and at a lower speed.
2 greatly reduces chine walking as well as porpoising.
3 dramatically improved handling and stability in rough water and crossing wakes.
I'm considering putting one on my 16 250hp etec to help with stability and slower planing speed.
A 4 blade prop will also help with quicker planing and at a lower speed, something else I'm considering.
I like the fact that they now offer tails that don't require drilling to install, that was the hard to do on that shiny new skeeter with that shiny new merc. but it was definitely worth it.