He died peacefully at his home at Grangecon, in County Wicklow, yesterday morning.
His son, Francis jnr, said: “He was a great man to me, a great man to the family and a great man to racing.
“He passed away peacefully at 4am this morning.
“He loved racing all the way through to the end. From riding to training, he was always up for it and absolutely loved the game.
“I haven’t switched the training licence or anything like that just yet, but I plan to keep the yard going.
“He will be sadly missed by us all.”
He is survived by his wife Teresa, sons Tom, Francis jnr and Kevin and daughters Brid and Mary.
As well as taking the blue riband of jump racing with Glencaraig Lady in 1972, Flood also won the Arkle Trophy Chase at the Cheltenham Festival with Bobsline in 1984.
He twice won the Irish Grand National at Fairyhouse with Garoupe in 1970 and Ebony Jane in 1993.
Flood, who was champion amateur rider in Ireland seven times, started training in the late 1960s and quickly established himself as a top handler, saddling the first two in the 1970 Irish Grand National with Garoupe and Glencaraig Lady.
Former Irish champion jumps jockey Frank Berry, now racing manager for owner JP McManus, recalled many happy years riding for Flood with many big-race successes, including the 1972 Gold Cup on Glencaraig Lady.
He said: “It’s very sad to hear of the news of his passing.
“I rode for him for 18 years. He started me off when I came out of my apprenticeship.
“We got on great and had some great times together. He was a marvellous man and it’s just a sad time.
“Our sympathies are with all the family.
“Winning on Glencaraig Lady was great for me. It was my first ride at Cheltenham as well. It was a huge occasion.
“We had a lot of good years together. He was a wonderful man to ride for and he was just a nice man.”
Another former top Irish jumps jockey who has fond memories of Flood is Charlie Swan, who gave the trainer a second Irish National triumph with Ebony Jane.
“It’s sad news. He was a lovely man and very easy to ride for,” he said.
“He was a gentleman and a very good trainer.”
Irish Classic-winning trainer Adrian Keatley has known the family for years and started off his life in racing with them.
“The Floods have been neighbours of mine for a long time and I learnt pretty much everything I know about racing from them,” he said.
“I started riding out there when I was 13, Francis was still riding out at that time.
“I worked there for many years and rode for them as an amateur in point-to-points and things like that.
“It’s very sad to see a legend like him pass away and my condolences are with his family.”