Fish finder problem - Cuda 350 s/map

End result:

I did the foam block/water method. I got a baster from walmart and used that to fill the chamber... then after the day on the water I used it to suck the water out...

I worked extremely well. I finally have a fish finder that works 

parts used:

-yoga step to cut the block from for the transducer
-marine goop to glue the block in place
-baster to fill/empty the chamber