Speed data management for google map app

Current google map application at [Removed by Freelancer.com Admin] loads all data for markers, 23 MB when the map opens, taking about 45 secs. I want to load only essential data to show markers when the map opens, and load full data for a pin when user clicks on the pin. Display of 1500 pins should take less then 5 secs. Also data entry form scrolls uncontrolably with some browsers; I want the data entry form to open in a larger window so that scrolling to enter data is not necessary.