Surely you can run a piece of 3/4" hose...
From the sink drain to the head intake line right next to the thru-hull, cut the head intake line and put either a tee or wye fitting in the head intake line, and reconnect the hoses without a diagram. Double clamp 'em all. There's not much way TO diagram that. How long the sink drain hose has to be, and the path it has to take depends upon how far the sink is from the head intake thru-hull and where you have to run to the hose to get there...and every boat is different. I can tell you that the sink and the head do have to be on the same side of the boat to do it. So just trace your sink drain line and find space for a new longer piece of hose to go through to get to the head intake thru-hull, measure it...if necessary buy a new piece of hose that's long enough...and a fitting. When you connect the hose to the head intake, the two cut ends of the head intake hose should connect to the top of the tee, and the sink drain to the leg. And remember to close the head intake and sink drain seacocks before you remove or cut any hoses!
