I have a 5hp long tail on my Grumman sport boat. It pushes it just fine I neal down in front of the rear seat on rubber mats. it gps's at 11mph with a worn down prop its like 5-1/4" not the 7" it's as new.Lots of good info. Thanks. I am sure the performance of the surface drives and American style short shafts are great, just really expensive.
The genesis of this project was wanting to put a long tail on my Grumman Sport boat. However, after a couple hours conversation with an old timer / owner of the same boat his thought was it would be less than ideal. ”Mud motors are made to be driven standing up.” Not too keen on driving my G boat standing up.