My boat is a 89 larson senza 210 lx 350 engine that had a over heat problem. I just put a new impeller in changed some coolant lines around and found a broken t stat. I cant get the stat out so i knocked out the center of it so its open at all times now.

The boat was running 160 to 180 and now it runs around 120*, is this to cold to run a boat engine

No reason you shouldn't be able to get the Tstat out somehow. I assume its corroded in????
If its a carbed engine, the 120* temp really should not hurt anything though. It should have a 140* tstat in it anyway if its carbed. EFI/MPI use a 160* tstat.