I'd say maybe for the 5400, but I'm still going with no on the 8000. But what I'm really concerned about is the Mamba 25 esc. I do not AT ALL think the Mamba 25 esc can handle the riggors of a boat. The load changes on the motor are just too far and fast. The esc isn't designed for marine use, but land use only. I can almost guarentee you that you'll burn that esc up running it in a boat, especially using the 8000.

But hey, give it a shot, I could be wrong. But if it were mine (and I do have the 5400 system in my 18t) I wouldn't let it get near any of my boats.