[Chris Burkard]

What engines and what year is the boat.

Clearly the alternator is bad or some component of the charging system is causing the alternator to lock up. I'm guessing the sound you hear is not bearing noise, but the alternator magnetic field overpowering the belts ability to turn the pulley and causing slipping of the belt. When it gets hot enough, the belt fails.

Early 31s used a traditional alternator and flooded cell batteries (lead acid). I'm not sure of the year, but at some point, Tiara switched to GEL batteries which require a different charging rate, so the standard internally regulated Alternators were removed from the engines when purchased and Bal Mar Alternators with external regulators were installed by Tiara. These alternators tend to have more issues than the standard internally regulated variety as they age. If you have a GEL battery system, you can't go back to a traditional alternator unless you convert the complete system.

Do you have GEL Batteries? This will tell us how you should proceed.

Sincerely,