Few people can say they've held a world record for 45 years. Far fewer still can say they've managed to do it in a vessel they built by hand.

But that was Ken Warby, who passed away peacefully on Monday from Alzheimer's disease.

He held the world record for the fastest speed achieved on water, a result he first achieved in 1977 when he raced across Blowering Dam in southern NSW in a hand-built boat.

On November 20, he clocked a speed of 464 kilometres and hour. A year later, he beat his own record when he registered a speed of 511km/h.

Since then, two people have tried to beat his record but both died in their attempts.

Sporting organisations, local businesses and friends and family in both Australia and the United States - where Warby had lived since the 1980s - have spent the week paying tribute.

The Australian National Maritime Museum, where Warby's record-breaking boat is displayed, praised his extraordinary achievement "powered by ambition, common sense and a tiny budget".

Fans hung an Australian flag by Blowering Dam in his memory.

"He was a one-off type of guy and very brave, and in the end very proud of what he'd done," said Sue Ransom, his former jet car racing partner.

She said Warby once offered to help her achieve the women's water speed record.

"I answered, 'I'd be after the world record'," she said, although in the end she declined as she was wary of the pursuit's high fatality rate.

Warby was born in Newcastle, NSW in 1939 and grew up racing speed boats on Lake Macquarie.

His childhood hero was Donald Campbell, who held the world water speed record from 1955 to 1967.

A mechanical engineer by trade, Warby built his record-breaking wooden speed boat in a shed by himself.

He raised the money by selling intricate landscapes he painted onto planks of wood, carved into the shape of the Australian continent.

He also crafted small toy boats and saved the profits to build his vessel, The Spirit of Australia.

Ransom said she believed it was Warby's long-term experience racing boats that allowed him to sharpen his intuition for water racing and the conditions required.

While other racers would wait for glassy water, he raced with a swell, which he felt would release some of the air pressure from the high speed and keep him safe.

In the end, this intuition, combined with his engineering, determination and ability to stay affable even under pressure, allowed him to go faster than any other human being has ever gone on water.

Later, he moved to the US, where he enjoyed racing speed boats for fun with his wife Barbara, who survives him.

Warby often returned to Australia, where he was building another boat to break the world record.

In recent years, his Alzheimer's slowed down his travel. But J MacCracken, his former crew chief and close friend, said Warby never let go of his sense of humour.

On a recent cruise, it took a while for Warby to realise he was on a boat.

When he did, he turned to his friend and quipped: "It's not going too fast. I'm going to speak to the captain to see if we can speed this one up."