Possibly a bit late now...............depending on what you have already done to the shackle!
But I do have quite a bit of experiance with frozen shackles from lifting mooring
chains from drying moorings as and when they wear out. Usually whilst standing knee deep in mud..........somewhat away from power tools.
The shackles (same size if not a big bigger than those used to attach a decent Anchor) are always rusted solid - quite often also coated in thick rust to the chain........and their is an incentive not to have to use a hacksaw by hand, cos' it be like wrestling an eel.
1) Hit the shackle with a hammer to knock off all the rust that will fall off, taking care not to distort anything or "seal" the screwed end (in practice no great difficulty as standing knee deep in mud yer cannot apply "full welly") - I suspect that yours won't have been this bad.
2) Use the largest monkey wrench that will still fit the shackle key end (don't mess around with the hole!)..........so you get lots of leverage - and use a large tommy bar (I have "special" f#ck off sized screwdriver just for this job!) fitted through the U part of the shackle to counter the force you will then apply. TAKE care with things slipping - you can end up punching yourself - fairly hard
Works 70% of the time. maybe another 15% comes from fitting extentions of pipe to the ends of each lever to increase the force (Luke
), but this increases the riskof twisting / ripping the shackle key end off and having to resort to the hacksaw . (Note: all percentages approximate
And a free tip when working in mud, take something to put yer tools in when you need to "just" put them down for 2 seconds......as otherwise they sink
Or sell 3 foot of Anchor chain end on E-Bay. Buyer collects