torstein

I had the same problem, and I used a long knife. I was laying under the trailer and a buddy helped me heating it with a gasol-flame.
The knife can be blunt, the trick is that you melt the rope. Dont heat it to much, fire-hazard. Let a buddy reheat the knife when kneeded.
You can do the job alone, but then you have to crawl upp and down under the boat.

In Sweden were I live there is a product called gasol, I think many call it LPG or Propane gas.