From 1949 until sometime in the early 1970s, speed boat enthusiasts raced in the Gold Coast Marathon, an unlimited race with as many as 13 classes from the Pelican Harbor Yacht Club at the 79th Street Causeway to West Palm Beach and back the following day. The brainchild of Sam Griffiths, founder of the Pelican Harbor Yacht Club, Griffiths himself was a powerboat racer who won the first Marathon and two others. Top finishers completed the first 67-mile leg in one hour. The very best drivers in hydroplanes topped 100 miles per hour in the fastest stretches of the race course. In later years, the Marathon moved to the new Miami Marine Stadium amidst safety concerns when scores of small boats entered the race. Toward the end, the Marathon garnered the sanctioning of the prestigious American Power Boating Association. The long-abandoned Stadium is now in the hands of preservationists who hope to restore the Stadium to its former beauty and style along with educational programming.
Florida’s Big Dig 
This race didn’t run to the early 70’s, I think they mean the early sixties, but was definitely one of the best races in the world !
actually I do not recall it ever being run in the stadium. when the Corp of Engineers said we could no longer race the intracoastal we went from Miami to Key largo and it was known as the Roaring 100
Ran in the Gold Coast Marathon 3 years in the 200 class for boats with max 30 hp. Finished 2ed in class twice.
Tom Stansbury: I got interested in hydroplane several years ago when I drove up the coast to interview a Ft. Lauderdale resident, Stu Wilson who won the 1956 GCM on the Intracoastal from Miami to WPB and return the next day. He passed away after, not because of, the interview. I have his oral history on DVD. His brother Don was more famous because he was one of the three who died on Black Sunday.
One of the three who died on Black Sunday. I recall he died in the collision of two boats vying for the President’s Cup on the Potomac River Basin. The third died in another race the same dad. Hydroplanes were never the same. William G. Crawford, Jr. “Bill”. wcrawford41@gmail.com.