I have a Hummingbird Jimmy Houston model that I use for icefishing and which is powered by a jel battery from Cabelas.
It works great ,maybe not like an Fl-8 but it only cost me $90.00
I mounted a bubble level on top of the transducer and made a bracket out of a piece of 1/4 " thick clear plastic which is fastened to a piece of 1/2" pvc tubing that is cut to fit between the mounting yokes on the transducer. this is held in place with a 1/4" bolt thru the pipe and tightened with a wing nut. This allows for adjustment when leveling..
I suspend the transducer off of 12" piece of 1/4" allthread which has one end screwed into a hole tapped into the the center of the clear plastic piece and is locked tight with a 1/4" nut .
I cut 2- 3" discs of 1/2" foam board ,put a hole thru the center and slid them on the allthread down to a nut and flat washer and then put another flatwasher on top which has a 1/4' wingnut on top of it .this allows for adjustment for thick ice by sliding the foam discs up and down the rod.
Secure the transducer wire to the allthread with a couple of tie wraps and you're ready to go.
The foam discs float the transducer like the more expensive one does and I can see my jig and bait in 30' of water.
Good fishin.....