Meaning of Phrasal verb "hook up"

Could you please tell me what “hooking up” means in the following dialogue (from Hemingway’s newly discovered short story "Pursuit as Happiness")?

“Hook her up, Josie!” I yelled. “He’s taking all of it.” [i.e., the marlin is pulling all the line out.]

“She’s hooked up, Cap. There he goes.”

As you surely see, ‘her’ and ‘she’ refer to their fishing boat and ‘he’ is the big marlin that has been hooked and is pulling the line out.

Meaning of hooking up is clear in sentences like “. . . forgot to hook the boat up to the trailer!” and “Did you ever hook the boat up to the tow vehicle?” but I can’t get the meaning of it in the above-mentioned dialogue.

It means full speed:

“[Go full speed], Josie!” I yelled. “He’s taking all of it.”

“She’s [at full speed], Cap. There he goes.”

. . . The reel was too hot to hold and the core of line on it was getting thinner and thinner in spite of the Anita going full speed after the fish.

“Can you get any more [speed] out of her?” I called to Mr. Josie.

“Not in this world,” he said. “What you got left?”

“Damn little.”

It appears to be era-specific (Hemingway's story is set in 1933) engine lingo. Search "hook her up" boat speed and "hook up the engine".

Here is some 1931 testimony from a New York Supreme Court Case on Appeal:

Q. Hook her up does not mean to put up a line on the boat? A. No, sir.

Q. Or to fasten her up to the boat, but it means to hook the engine's valve up, so that she has full steam, and that means, in other words, full speed? A. It gives that word to the captain, to the pilot house, and he maneuvers it with bells to hook the boat up to work it on the ship.

Q. (By the Court:) So that it will go fast, is that it? A. Fast, yes, sir.

Q. So that when pilot Shooks on the bridge of the steamer said to the tugboat to hook her up, he was giving her an order to go full speed ahead? A. Yes, sir.

Here's an excerpt from Zane Grey's An American Angler in Australia (1937):

"There's a fin!" yelled Bill, suddenly. He was up on deck. "Far ahead and going fast."

"Chase it," I ordered. "Hook her up, Pete."

We ran down current like the wind . . . Peter saw him again and that encouraged us. He opened up the engine full ahead and we roared over the swells, leaving a white wake behind us.

"There he is!" shouted Peter, pointing. "Going like one thing!"

"Don't run him down, Peter," I said, as I caught my first glimpse of the big gleaming tail fin. "It's a black Marlin."

Peter slowed down. But we had to go at least at a ten-knot speed in order to come up with the fish. His tail went under, came up again, flashed opal and gold, vanished, to show once more.

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Further reading: Hooking up the engine