I just bought a 18 ft boat with a 70hp Yamaha for a great price. The guy I bought it from told me that it runs great but it is hard to start. Well I took it home and it started right up. So I took it out twice since then and both times it gave me trouble starting right when I put it the water. Once I get it started I can shut it off and fish for an hour and turn the key and she starts right up. Any suggestions on what I can do to solve this promblem?