Quick question. On the back of my Scarab I outdrive; right where the upper and lower unit meet; bolted right above the Alpha drive center tab is what I would call a "whale tail".

I assume that it is to get the boat on plane faster but I don't know? What is it's purpose? Does it hurt my top speed?

I hope I describe this good enough. Any help would be geat; want to know whether to keep it on or take it off.

If it's an after market "fin" I would get rid of that thing!!! Supposed to help with low-end, but will hurt top end. And that cavatation plate isn't really meant for the extra load anyway.

Like t500hps said, it's designed to keep the boat on plane at lower speeds.
They will cost you both cruising and top end speeds, usually by a substantial amount.

Yank it off as fast as you can and deny ever having it on there....

This makes sense for me why it is on there since my boat was a stunt/prop boat. Was wondering why the boat wouldn't do past 50. It's off today!!!

Thanks for all the help.

Tail.......what tail......