MARION — With 35 pounds of gear on his back, Marion Resident Chad Santello plans to walk the notoriously hilly Boston Marathon course on Oct. 3 to benefit fellow soldiers and first responders.

Santello , who was stationed in Iraq, is participating in the “Tough Ruck Boston 26.2 for the Fallen.” He’s no stranger to marches like these.

“I’ve done a 25-miler while I was in the army,” he said. That was two years ago, and Santello said he was in worse shape then than he is now.

He’s been logging about 10 or 20 rucking miles per week to train for the tough ruck.

“Rucking is really learning to suffer for a while,” Santello said.

But, he said, it’s for a good cause. Santello has already surpassed the $1,500 fundraising mark he committed to for the ruck. Now, with $2,537 raised as of Aug. 31, he’s looking to double his commitment before the ruck.

Santello is raising money largely online, through a page connected to his registration for the ruck. He said that so far, the donations coming in have largely been brought by word of mouth.

With all that money raised, there’s a lot riding on Santello finishing the ruck.

“You remember why you’re doing it,” he said. “If you don’t finish it, that money isn’t going anywhere.”

So, when the going gets tough, Santello said he’ll remember that the ruck isn’t about him.

“Put your head down and keep going,” he said