Bottom line is the tail fins have their place in light weight boats that are stern heavy....normally weight can be shifted to help the boat get up on plane more quickly!! Some folks refuse to try the balancing act and sometimes there is just to much weight at the back when the driver sits back there. If all else fails, the fins can be an advantage, they do work when used properly!
They get a bad name when folks use them as a short cut and the fin is used where it doesnt belong. Many folks buy smaller boats then put large heavy motors on the back, or for a fewvyears mfgrs added I/O's in small boats because they were cheaper than outboards. Many 16' runabouts had 140-175 hp I/O's installed as speed demons.....but they were very stern heavy, then the mfgrs added jump seats in the back for more seating capacity. However adding two heavy adults to an already stern heavy boat was a poor performer !! So the easy solution was to add a tail fin....at speed they worked well but at slow speed not so well, so people tried making them bigger to work at slower speeds. This added drag caused cav plate failures where higher hp and heavy weight were present. When used on smaller motors on lighter weight boats where weight distribution is not feasable, they do work !! Used them numerous times, but I typically made my own. As a toolmaker for many years it was simple and minevwere smaller and made from SS creating far less drag than some of the monster fins you will see out there today.
Like most anything, there is a time and a place to use one, when you exceed the design capacity, something has to give, this is where most complaints come from.
