I have spurs, the only time I am aware of having used them was when I was playing with my new asymetric spinnaker
and let the slack sheet into the water
. Of course it got tangled around the prop. Needed to replace the sheet, it was now too short.
My younger brother had spurs on his Four Winns powerboat in the Great Lakes
. He managed to cut, oh say a half dozen, anchor
lines while leaving the anchorage. I'm not surprised.
Lots of crab pots around here but I try to weave between them, a full keel
helps too. If I cut any, I'm not aware. On my last boat a polyproplene crab pot line got tangled on my prop. It cut itself off but the plastic line melted into my cutlass bearing requiring it to be replaced.