After I melted one of the standard connectors I was using on 2ea 7.2v 4200 ma battery packs with a series harness in my boat, I replaced all connectors up to the motor with Deans Ultra.
Just bathtub tested my riverboat, which is a hand made 32" hull equipped with a Graupner scale jet drive with a 2"1 belt drive reduction and a 700 series motor. The jet drive is now so intense it btasts 6 inches higher than the tub rim. Can't wait to try full speed on the lake.