Ok, let me get this straight. You want to use both batteries at the same time? If so, wire them pos to pos and neg to neg. The problem I see with this is,,, your locators will get interferance from one or both. Also you still may run the starting battery down till it won't start the motor. But with a 9.9 I'm sure the rope will start it. The charging system on a 9.9 will NOT recharge enough not to have to recharge after each use. Trolling motors that have speed numbers, as 1 thru 5, drain the batteries MUCH faster than those that have varaible speeds. Logic is fine and the deep cycle batt. will have enough cranking amps to start the 9.9. Use 1/0 battery cable to make the connections. Hope this helps and Good Luck fishin' <*)}}}><
You'll see the difference,,,on the end of your line! PROUD MEMBER OF TEAM GEEZER