"We didn't realise how big it was really until it hit the deck," Thorp said.
"I definitely wasn't expecting it to be a grander."
Thorp said he had always joked with mates that if he ever caught a grander he would retire.
"So they are all teasing me now, asking when I am finishing up."
Thorp had been fishing alongside Brendan Gardiner on the south side of Rarotonga when they hooked the marlin.
"You are always hoping to win but you never know your luck," Thorp said.
Hauling the fish in was a battle that spanned hours.
It was fine for the first three hours, when the fish was actually swimming, but when the fish died it became a real struggle, he said.
"With a fish that size you sort of give up. You think there is no chance anymore," he said.
"We were fishing in deep waters. When they go, they just keep going down."
In the end mates who were also out fishing - Papa Buckley, Buckley Jr and Thorp's brother Kieran - helped the pair haul the hefty marlin onboard.
The fish hit the deck on Thorp's 20 foot Poti Marara style boat, which he built by hand himself, under a car port with the help of a few mates.
Thorp said he had the utmost respect for the massive fish and felt that most importantly the catch had "put our little island on the map".
"It's gone viral online and a lot of people have never heard of this place," he said.
"So hopefully it should send a few people this way."
The fish was the heaviest marlin caught in the competition and Thorp won $1000 in prize money as a result.
Thorp runs the Facebook page Fishing Rarotonga with his brother.
🔥🔥🔥🔥The Grander🔥🔥🔥🔥
With one last excruciating heave, 2019s biggest sport fishing marlin in the world slid over the...
Posted by Fishing Rarotonga on Thursday, 6 June 2019
