They keep popping up everywhere and in high numbers without any pause - there is a bounty hunter fleet chasing me every second I am on the map, even with a very small bounty.  On many occasions multiple ones pop up at the same time.  Then they keep charging into the harbor with a tiny snow etc, their ship starts turning around and starts fighting against absurd odds like one fort, two npc first rates, the 3rd rates and frigates in my fleet and numerous other npc ships until their ship is destroyed.  They don't surrender and what's worse I cant board their ship either. (bugged?) Attacking them causes my bounty to rise in the first place too. If I don't attack, the icon for being able to go to the map shows, and if i go to the map their ship is still on the map and triggers the fight again. So it causes a loop if I don't attack.

In the city its even more unrealistic - every ~5-10 minutes 2-3 bounty hunters pop in the middle of all the city guards and attack my character who is a privateer of the city's nation. And when they are beaten, Im in criminal mode despite having been attacked, my own nation's npcs in the city cower from me and I have to get out of the city and reenter to avoid that. When I exit the city to fix it, I get a message saying "You were unseen avoiding the alarm" - as if I was a criminal sneaking in and out of my own nation's city. (another bug?). If I stay in the city instead and attempt to talk to a npc, it turns the entire city hostile and all the guards attack me to boost.

Is there any way to turn off this irritating and unrealistic - and buggy - mechanic? If not in the game menus and mod options, can I do it by modding game files?

That is an original COAS feature and we did not add an option for that, so you will have to edit a file:  Program\scripts\bountyhunters.c

Near the top, change this line to "return" from the function early, without processing:

void SeaHunterCheck()
{
    return; //Add this line
    int    j, i;
...
...

Also, in file, Program\loc_ai\LAi_login.c, line 259, comment out LandHunterReactionResult(location):
...

       LAi_CreateEncounters(location); 
       //LandHunterReactionResult(location); //Commented out with double slash in front
        CopyPassForAztecSkull();
    }
...
...

Thanks. Will this work for ongoing games, or do I have to start a new game after modifying that file?