My 81 Mercruiser 470 has been a money pit. Now the motor will start and run fine. But, once I shut it off I cannot get it to restart unless I wait for a while. When I first start it it sounds string but once it is shut off and I attempt to restart, it sounds like the starter cannot spin the flywheel. Like there is not enough power from the starter. The boat has been converted to an alternator and it charges at 14 volts. Is this a problem with the starter?