Have you looked at "newer" used motors? $2K should get you a long way towards something newer.

If you do have some work done on it, I would skip the rebuild and have them do the carb work and possibly clean out he carbon. When I rebuilt the carb on my Yamaha kicker the before and after difference was night and day. According to my mechanic the most common problem with the Yamahas is fouled carberators due to the pinhole sized orifices inside.
JMS