I'm not certain as to who's mooring line you're using, yours, or one permanently affixed to the ball. But I reckon you can figure out a way to make the following work either way.
You just get a section of PVC pipe or conduit, & slide it down over your mooring line, & you should be good.
Just make sure that you pick up a piece which is stiff enough for the job. As a heavy boat may snap a piece of 3/4".
I always made certain that the end of the pipe on the mooring ball end rode
on the fat, tail end of the splice in the 3-strand (from where I'd spliced in an eye), just on the off chance it wanted to chafe. But in 500+ days of life moored that way it was never an issue. And on the inboard end, I just made sure that my chafing gear
was set up to cover any rode
at that end of the PVC, as well as the standard stuff from mooring/anchoring. But again never an issue.
Oh, at the top end of the PVC, you can put a figure 8 or other stopper knot/system, so that you don't wind
up accidentally donating it to King Neptune (and or drill a small hole through the PVC & affix a small diameter safety
cord to it). And above the stopper knot
, I just slipped a fishing
float onto the line. One of the ones which looks basically like a foam bullet with a hole through the center.
That way, assuming that I didn't leave the dinghy
on the mooring when I took the boat someplace, I could leave the piece PVC on the line & it'd stay afloat for when I came back.
Also, to keep the dinghy from bumping me from the back, I'd just toss a small drogue
, or bucket on a short line off of it's aft end. Which I'm sure helped to keep me from bumping the mooring ball as well.