Turn the auger to move the chain until the master link is positioned on top of the boom.

In this position, the link is easier to access and the chain is braced against the guide on the boom.

Place the smaller, flat end of a 3/16 inch pin punch against the end of the master link pin that previously held the cotter pin.

Hit the larger end of the punch with a heavy hammer to tap the pin out of the master link.

Be very careful to avoid hitting your hand. Don't hold the punch too close to either end, and realign the hammer and punch after each swing.

If the pin is stuck, it may help to apply some kind of penetrating lubricant to the interface between the chain and the pin. Allow the lubricant to sit for a few minutes before trying again.

If you are still having trouble, a two-jaw gear puller or in-line pin puller might work better. When using a gear puller, it might be necessary to stabilize the claw side of the puller with some kind of spacer that won't be crushed when you start pushing the pin out. A 3/4 inch socket works well.

When using a gear puller, the master link has to be underneath the boom to allow adequate space for the puller arms. Turn the auger to move the chain so the master link is positioned properly.