When I get a particularly groady looking line, I just toss it into the 5-gallon
bucket of boatwash while I'm scrub brushing the boat.

By the time the boat has been soaped down, there has been enough "agitation" in
the bucket to clean the line up a lot.

Spread the soapy line on the deck and rinse it off when rinsing the last
section of the boat.

Not as fancy as using a front-loading washer, but it doesn't involve schlepping
lines off to the laundromat or home to the family machine. Sticking a slimy
green line into the Maytag may require a spouse with
reasonably tolerant standards.