I did have one on my boat but took it off.  It just mounted to the motor on the bell housing with 4 bolts.  Now I'm going to either save this one to be thrown away at a later date or cuss it every time it's in my way.  LMAO!!   

Here's what I do have and hope it helps.

 

Buddys Rogers

Same hook up.  I think this is the strongest way to put in a tow bar.  I've seen them through the fiberglass but then you have another hole in the boat.