Since my 2011 191 F&S does not have access to install a backing plate, what is the best way to install a downrigger mounting plate? I see some threads about toggle bolts. Not sure what they are or what they look like. Any ideas would be appreciated.
I use these: Scotty Gimble Mount. You could get the same ones for the Canon's, if you have those. I've run them for years on both a 215cc and 235c with no issues. There is a void where you place a piece of starboard for reinforcement. Works like a charm. Just mount the swivel head to the base and presto-magico.
Here's a photo of mine: No holes, no drilling, no backing plates, etc., etc.
I can not speak for your boat, but when I was installing the mounts for my outriggers I had to clear out foam all the way to the top my my gunnels. I had to make room for the mount and so the togglers could open under the gunnel.
My method allows me to remove the downrigger completely, leaving nothing behind, when we rig for tuna, or for storage. The toggles work, with prep as others have stated. Just make sure you get the stainless ones.
Careful about using rod holders for downrigger mounts. They are not thru bolted into the gunnels and a typical downrigger being trolled can easily exceed the holders fasteners. I use Cannon electrics and made up my own mounting plates that bolted in across the rear corners and then used cannon swivel mounts bolted through the gunnels. I did cut an access hole and install a removable plate as Harper suggested above.
All in all I could tow a boat with my downriggers.
JerryD, You should look up "toggler" and see how they differ from the common "toggle" bolt. They come in SS models and are made to be used in tight spaces where access is limited. I used them on my boat for the down riggers and the kicker motor mounting plate. They are very strong.
My down riggers are used for deep trolling with 17 lb. home made weights on Canon units with swivel bases. They are mounted to the gunnel using one toggle in the center of the base plate and then four heavy SS screws that go through the base of the swivel bases then the corners of the base plate and into the top of the gunnel roplene. These installations are rock solid and have not moved in over ten years of heavy use. There is a thread on my install with pictures if you are interested.