A former medical professor and associate dean at New York's Cornell University, he looks strong and fit - and he had been aware that he wanted to "retire into something" when he stopped working.
When he was 65, two of his adult children suggested he join them in the New York Marathon. His first reaction was "I'm too old for that" but he entered nevertheless. The younger Webers both picked up injuries before the event but Weber completed the 26 miles and loved it. He did more than 30 marathons across the US and world before getting into triathlons. In 2008, he entered - and won his age group - in the Florida Half Ironman leading to an invitation to do the full version. At the age of 70, he was hooked - and says his proficiency for pain is partly due to genetics.
"I like to say I selected my ancestors wisely," laughs Weber. "But I do think having a decent gene set is a pre-condition. You also tend to find that a lot of senior Ironmen have come to the sport later in life."
Weber's season seems almost non-stop - "often I don't know whether I'm training, recovering or tapering" - and he prefers to keep in top condition by competing. His summer schedule in New Zealand makes the eyes water. After competing in the Perth Ironman last month, two weeks ago he raced the Port of Tauranga Half Ironman. Last Sunday, he did the 10km Epic Swim on Lake Taupo and today he competes in the second edition of the Auckland 70.3 event. He has also entered an Olympic distance triathlon at Kinloch (February 2), as well as the Huka River swim (February 8, 3.3km down the Waikato river) and the Cross the Lake swim (4.2km across Lake Taupo) before the Taupo Ironman on March 1.
His triumph in Kona last year was special. The event is notoriously gruelling and many competitors decades younger than Weber fail to complete the Hawaii event.
"You need to be alert to pain but you learn to differentiate between aches of endurance versus genuine injury. Much of what we do is in the mind. People think of Ironman as a physical endeavour, and of course it is, but it is at least half mental. You have to be a persevering S.O.B."
Weber has a fierce but friendly rivalry with retired Rotorua farmer Neil Fleming (77) who took out the Taupo Ironman last year but came second (by three minutes) to Weber in Kona last year.
"I have a great battle with Neil," says Weber. "We are very supportive of each other and great friends."
The oldest person to complete an Ironman was an 83-year-old in 2012. Weber is not sure if he will still be going at that age - "something else might come along" - but you sense if he wants to surpass that record, there is almost no doubt he will.
