On the boat in question, the owner had recently installed high output alternators. Not a bad thing necessarily. But, in this case the higher output units were a bit larger physically that the original equipment alternators. No surprise there either. Well anyhow the installer had mounted the new units and adjusted the drive belts to an appropriate tension. In the process of doing all of this the stud on the back of the alternator that is normally labeled B + had a boot installed, but to achieve proper belt tension, the alternator had been pulled into a position that wedged this boot up tight against another metal component mounted on the engine.