So i bought a 66 evinrude 6 hp. 6602 e is the model number. The guy showed me it ran great which it did. But once i got it on the water i found it would shut off after running a bit. I found this to be because it gets thrown into gear basically. It will only start if i rotate the prop which allows me to move lever into fwd reverse and neutral. However once it runs for a minute it will on go into 2 of the 3 until i move prop. What could be wrong?