I have a 1989 200h.p. yamaha the trim motor works intermittently , I can initiate the running by gently tapping on trim cover.The motor sounds a little weak when engaged.Assuming corrosion inside or brushes starting to go.Question, can brushes be replaced or does trim motor assembly have to be replaced?If the entire unit has to be replaced, does the engine have to be removed?Any idears of where I can find replacement parts including the entire assembly?Thank you