can you hook up a trolling motor to an out board
The idea of locking the trolling motor ahead and using the big motor as a rudder would work.
How about this... Think of those linkage arms you can get that connect your big motor to a kicker. Build your own. Same concept here. Get a large enough piece of PVC that fits over the handle of the trolling motor. Connect that to a piece of conduit, half by half, etc. This is your steering linkage. Connect that to the main motor. Voila... problem solved. It should take maybe 3 screws/bolts at most. A piece of PVC which isn't expensive at all. And a long enough piece of conduit/half by half, etc. which also isn't going to kill the wallet. And maybe a few other simple things that you probably have on hand already to make the linkage connections. That's it... Trolling motor isn't completely modified. To stow the TM when making a run just slide the PVC off of the TM handle and stow it.
Cheap, simple, should be able to build it for less than $20, and it would take very little time to build.
Get a 4" PVC toilet floor flange. Turn it upside down so the pipe goes up and trim to fit on the anti cavitation plate. Add a few inches of 4" PVC vertically. Then cut a 4" PVC tee in half to form the cradle and mount this to the 4" vertical PVC. Add trolling motor and hose clamps and troll away!