Humminbird Makes the Pirahnamax series for us cheap boaters. I have the 150 which retails for $79.99 but if you go up to $100 you can get the 170 which has better sonar.
Used fishfinders from what I've seen can't be had much cheaper if any than these units and used doesn't give you warranty and usually means rigging some portion whether hacked wiring or broken mounts, etc......
These Ebay things are even worse. I bought one at Harbor freight a "Fisherman's Habit" with a gift card and sale it was like $25. Didn't know how bad it was until I ran it next to the Pirahnamax. the Detail of Humminbird's Cheapest unit blew that away.
all the brands seem to have inexpensive basic units don't think you can go wrong with any of them and like I said about the used units you will probably get your $$$ back down the road if you want to upgrade and put it on CL
Good Luck!
