In short - no. They all rely on basic o ring set ups that at some stage seem to let water in. Something that may be worth considering is fitting a cable entry similar to what is used on ships - basically an inverted "U" - bit like this
http://klober.co.uk/shop/product/flavent-cable-outlet
either big enough to pass an Anderson connector through into the anchor well corner to start with preferably just in case you ever get water in. It could be made smaller by leaving the ring terminals on the motor and bring it into the cabin onto a pair of posts with wingnuts.