I go against the grain of most on here. I use hairy polyprop because it floats and will never wrap itself round a prop. It's also cheap as chips when bought in a 200m coil. To my surprise it hasn't shown any sign of chafe in the 15 years I've been using it.
Having said that, I only use it when away from home. On my mooring bridle which is exposed to the elements 24/7 I use 20mm green fishermen's line, also polyprop but green and shiny. I replace that every 5 years - 11m @ 95p/m. last of the big spenders. That isn't suitable for dock lines as it's stiff and shiny so only suitable when spliced.
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