Outer bands of the storm hit early on Saturday morning in the Guayamas area, 60 miles (96 kilometres) from San Juan, the capital, on the southern coast of the island.
Marco becomes category 1 hurricane south of Lafayette
Wind bursts downed trees and power lines, leaving thousands without power, buffeting the island's power grid, which remains fragile after storms and earthquakes have hit the island repeatedly over the last three years.
Some roads were flooded, making travel hazardous and hampering the operations of relief crews trying to clear storm debris and restore power.
The storm is headed for the island of Hispaniola, which is shared by the nations of Haiti and the Dominican Republic over the weekend.
Authorities in both countries have issued storm watches in anticipation of winds and rains, which could prompt flooding in the heavily populated coastal regions, and dangerous mudslides in the mountain areas.
Video above from previous post.