Nice little boat you have. I had 10 feet + 3hp for a while.
Regarding fish finders. Try to get descent unit from first time. I've been through 3 of them and still looking
(H. Piranha MAX 20, H. 565, H. Matrix 47 3D and now looking at H. 797 c2 SI )
My opinion is Lowrance makes better vertical units (object separation, distance on which object could be detected, etc). Humminbird is a king of 3D sonars. I like SI units very much.
If you are buying 2D vertical, try to spare $$ for a color one with a 5" screen.