I have an aluminum 17' Smoker Craft canoe from the mid-60s. It has some VERY large dents in it (e.g., 2' wide and 6-8" deep, mainly on the bottom of the canoe). I only use it on my pond, but the dents are still an issue. Originally they were from rocks, but since we moved up by Lake Superior they are from 3-4' of snow building up on it over the winter (I keep it upside down and outside). I don't want to try to bang out the dents for fear of damaging the canoe / metal fatigue. Any suggestions for getting the dents out otherwise? Piling heavy weights in it?

I took a couple of good size dents out of my 16 ft alumacraft with a hammer. Use a piece of wood over the dent, hit the wood with the hammer. A couple of strong blows did it for me.

Just hit it with a big log or 4x4 to pound out dents. If it cracks the aluminum you will need to just weld it up at any welding shop. Really easy to do. I’ve don’t this on snowmobiles, canoes, and fishing boats. You need another person on the other side with another solid block or on the floor with a chunk of wood to absorb the hit.

What has been said above is true. As someone that fixes boats for a living, you'd be astonished what an alum boat can handle. Don't use a steel hammer; the wood suggestion is the way to go.

Or BIG rubber mallet.
CB

bassmeister: "I have an aluminum 17' Smoker Craft canoe from the mid-60s. It has some VERY large dents in it (e.g., 2' wide and 6-8" deep, mainly on the bottom of the canoe). I only use it on my pond, but the dents are still an issue. Originally they were from rocks, but since we moved up by Lake Superior they are from 3-4' of snow building up on it over the winter (I keep it upside down and outside). I don't want to try to bang out the dents for fear of damaging the canoe / metal fatigue. Any suggestions for getting the dents out otherwise? Piling heavy weights in it?"

Funny, I have a 17 foot Smokercraft with the exat same issue.

My wife and I hung an aluminum Starcraft canoe against a rock in middle Tennessee's Roaring River in the early '70s. Damage was limited to the hull; the gunwales weren't bent. We set the canoe on a grassy section of lawn and jumped up & down in the boat until the hull was properly contoured again. We got lots more years service from the boat (and learned an important lesson about whitewater paddling).
TZ

I have popped out some big dents with blocks and a small hydraulic jack.

Lots of suggestions and good ideas. Let us know how this turns out for you Bassmeister.