From Makarska to Kotor there is a driving distance of about 245 km following the shortest route, during summer season it is possible to travel with direct bus between the cities, bus travel time is about 5 hours and 30 minutes. If the direct bus should not match your itinerary you can also travel from Makarska to Dubrovnik and then catch a bus between Dubrovnik and Kotor from there, which should give you more travel options.
Timetable Makarska to Kotor we have listed below, if you wish to see departures in the opposite direction you can do so here.