I want to mount side scan and down scan on my jon boat(17’).
Someone stated not to drill into transom.
Will some one enlighten me on this?
By john boat I’m assuming an aluminum boat. Most have wood transoms, drilling could allow water to soak in and rot transom. Put some 3m 5200 behind mount and into drilled holes for mounting screws and you should have no issue… Until you want to take it off. 
Not sure -haven’t looked if the transom is wood… Need to look. It’s a 2006 Duracraft.
I plan to mount a piece of starboard and then mount the transducers to that. Seal all w/ 5200…
DRMajor
Epoxy something on and screw to epoxy
More than likely wood sandwiched with aluminum. You’ll be above and beyond the average install with the added starboard. Just take a peek at any John Boat at a gas station or landing. Most people don’t go the extra step. I’d also recommend using a transom saver during transport.
My bottom 3rd is Alum with vertical stiffening ribs & the top 2/3rds is 2 layers of 3/4" plywood with Alum on both sides. I mounted mine in the bottom 3rd & used 5200. No issues so far, I will have to grind off bolts if I ever need to change but it’s not going any where.
My hope is that bolt/screwing starboard (or other material… Starboard is $$$) to the transom, it becomes the sacrificial material and saves the transom.
If I need to change items, they will be in the plastic and not aluminum.
DRMajor
Scuff your aluminum and spread some epoxy on it and scuff some PVC board and epoxy it together. Then screw your trancducer to the PVC board and put some adhesive like epoxy on the screws for extra holding strength.
If you’re keeping it get a welder to weld a “U” bracket to the transom for transducer mounting.Most of the newer aluminum boats are like that now.
It has one way off to starboard. Only room for one transducer.
DRMajor
Took a look at transom and Duracraft has an ALL ALUMINUM TRANSOM label on it… Nice/
DRMajor
DM, be aware that Jon Boats don’t have a clean bottom. Don’t be surprised when you get going and lose bottom/depth reading.
Could be 10, 15 or more mph. When depth is blinking, it’s not thinking. Have a Garmin.
NN