missing fin above prop

[tfrewen]

I am new to outboard motors, so this may be a dumb question, but if I don't ask I won't know. I have a 1989 Mariner 115hp outboard. There was a fin on the lower gear case that is just above the prop. It was broken off when I bought the boat. It looks like it will rotate left or right, my guess is to help with steering alignment. Can anyone tell me what it is called and where I might find a vendor that can replace it.
Thanks,

 

[Plainsman]

Re: missing fin above prop

It's called a Trim Tab. A google search will find places to get one.

It helps to balance steering torque.