Ramsay posted a 6-under 65 in the first round but had three bogeys against two birdies Friday in moving to 5-under 137 after 36 holes.
Gregory Havret, who took a double-bogey 7 on the 11th hole (where had had an eagle Thursday), is second at 3-under. He shot even-par 71 Friday with four birdies, two bogeys and the double bogey.
Sergio Garcia had a steady -- two birdies and one bogey -- 1-under 70 and is in third place, three strokes behind Ramsey. Miguel Angel Jimenez, at 1-under, and David Lynn, at even par, are the only other players not over par after two rounds.
An indication of how differently the course was played Friday was the performance of Ross Fisher. He was in second after the first round at 4-under despite a triple-bogey but Friday he shot 8-over 79 without a birdie and plummeted into a tie for 21st.
Ramsay was 2-over after six holes but got back to even with birdies at 8 and 11. However, he closed with a bogey at 18 to settle for the two-stroke lead.
Swim Week Miami Beach 2014 [PHOTOS]