An exhausted Jeff Horn is confident he'll regain his strength in time after narrowly making weight for his maiden WBO welterweight title defence against England's Gary Corcoran.

A gaunt-looking Horn tipped the scales at 66.52kg [146.6-pounds] at Tuesday's official weigh-in - just under the prescribed welterweight limit.

It amounts to a loss of nearly 4kg [8.8-pounds] overnight and while trainer Glenn Rushton said he made it "very comfortably", there were some private concerns inside the Horn camp that didn't dissipate until the right numbers came up on the scales.

Gary Corcoran's minders didn't help their nerves, either, by complaining about the accuracy of the measuring equipment and forcing organisers to quickly find a new set of scales to appease them.

Horn will spend the next 24 hours refuelling and rehydrating and will be several kilograms heavier by the time he steps in the ring.

"I'm very relieved," Horn told reporters.

"It's always good to get in nice and close to that weight but not go over it, because it can be stressful.

"It's always a struggle ... (but) I've done this plenty of times before. I feel like I'll be feeling good tomorrow.

"I'm going to have a good feed tonight and just relax, watch a movie, have a nice sleep, get up and do the business."

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Corcoran's co-trainer Peter Stanley suspects such a dramatic drop could drain Horn of energy in the later rounds.

"No doubt, he had to suffer," Stanley said.

"The more times you go to the well the more times you're going to struggle.

"I'm not saying he's going to struggle - tomorrow night he's going to be a big, big boy, another five or six kilos for sure.

"Will it make him suffer in the fight? We'll see."

Corcoran had no such troubles, weighing in at 66.47kg.

The stakes for Wednesday night's fight at the Brisbane Convention and Exhibition Centre are enormous for both fighters.

The winner is slated to meet arguably the world's best pound-for-pound boxer, Terence Crawford, in a multi-million dollar bout next year in Las Vegas.

Corcoran has been installed as a rank outsider and the 27-year-old has never fought outside the United Kingdom before.

Having spent the last three weeks training in Brisbane, Stanley believes he is in tip-top shape and confident his charge won't be overawed by the occasion.

"There's just no way that's going to happen," Stanley said.

"We've fought away from home before in front of bigger, more hostile crowds against bigger boys. There's nothing new here."