Wel thanks for the fast and goods replies ! Well i was not hoping to keep the battery pack, i just put it in the shema to show where it goes :P And you two confirmed my idea of changing the motor! Changing the ESC is a good idea. I cheked at hobbyking and there alot of good stuff ! But ill need help to find the best ESC and Brushless motor. And i also wanna know, is water cooling necessery? Will a vented area will do the work ? The boat used is in the attached files, its my dad's boat he ran over year and its now mineSo thanks for the advices ill check the topics often to see if anyone have other ideas !