What I wanted it for
redoing the painter lines on my canoe. wanted something stronger than regular ol’ rope. And I just like Spectra
Bad idea IMO
Even if you are careful and keep the painter bungied down when not in use, there is always a change you’re gonna get it wrapped around something or someone at a very inopportune time.
When it’s wrapped around your leg in a fast current and you accidentally drop your knife as you go to cut it, you might be wishing for regular old rope, or something that is at least going to break before it tears your leg off or tears up your boat.
Use rope that is appropriate for the value of the equipment and for safety. A painter is for pulling the boat around, which normally wouldn’t put more then maybe 50 lbs of force on a line. A rope that can handle 2 to 4 times that max load will be more suited to that use and it’s not going to rip your boat apart or tear your appendages off if/when things go wrong.
Just sayin… 
jim
totally
carry a large throw bag of a spectra core rope and suitable accessories for boat extraction in a worst case scenario and a thick high quality braided polypropylene for painters. like the stuff found in the large North Water throw bags. my 2 cents.