Motor Problem

[Smalls]

Alright so I've been working on my pawpaw's boat for about a month now, with alot of help from my dad and bro. Biggest problem with the motor, other than the fact that it is 16 years old and hasn't been maintained the way it needs to be, was a bad starter. So, I got the starter rebuilt. Ever since, the boat has started great--except for two instances on the water. So, now i'm trying to figure out what the problem could be. The first time it seemed like it just wasn't getting gas, because after several attempts to start it, it finally did--after about 30 or 45 minutes that is. But the second time, couldn't get it to start until after I had pulled it out of the water. Anyone got any ideas or experience with this problem? The motor is a 1995 Evinrude 25 hp.