I am thinking of adding a TM to my boat in the future, but I don't want to add a second battery. Right now I have a group 29 everstart maxx battery from walmart. It starts my motor, and runs my livewell pumps(1.5 amp) and bilge pump when needed (never needed yet). Lets assume my motor didn't have the alternator, or I didn't start my motor all day. How long can I realistically expect to use the TM and still have enough power to crank up the motor? If I buy a TM it will probably be the motorguide varimax 40lbs thrust at walmart for $200, unless someone has a better suggestion for the price?