Equipped with blinkers for the first time he raced in second behind the runaway pacemaker Park Lawn before taking the lead on the final turn, but was overtaken in the straight and finished third behind the 33/1 outsider Weaver's Hall and Ragapan.
[3] The blinkers were left off when Buoy started 11/10[4] favourite for the Great Voltigeur Stakes (a trial race for the St Leger) at York Racecourse in August.
His opponents included Ragapan, Duke of Ragusa, the Epsom Derby runner-up Cavo Doro and the French challenger Valuta (Prix Kergorlay).
He took the lead two furlongs out but was overtaken by the 28/1 outsider Peleid who won easily by two and a half lengths, with Buoy holding on to second place, just ahead of Duke of Ragusa and King Levanstell.
At York in May he was moved up in distance and started 11/8[4] favourite for the fourteen furlong Yorkshire Cup in which he was matched against the seven-year-old Petty Officer, at that time the highest-earning gelding in British racing history.
[5] Buoy tracked Petty Officer throughout the race before accelerating clear in the final furlong to win easily by three lengths with the St Simon Stakes winner Ballyhot in third.
With all five jockeys instructed to employ waiting tactics the race was run at a very slow pace before Mercer opted to use Buoy's stamina and sent the colt into the lead.
In the Hardwicke Stakes at Royal Ascot later that month, he failed by half a length to concede four pounds to Relay Race, rallying strongly after being headed in the straight.
[6] There was no International Classification of European three-year-olds in 1973: the official handicappers of Britain, Ireland and France compiled separate rankings for horses which competed in those countries.
[3] In the British handicap for 1974 Buoy was ranked sixth among the older horses, level with Ragstone and behind Dahlia, Admetus and the sprinters Blue Cashmere, New Model and Singing Bede.