DONE!

A little creepy feeding the hose through to the head side hole, man that sucker is so small. If they'd made that hole the same size as the aft hole, it woulda been a LOT easier. Since the hole isn't sealed, anything that spills in the port locker is goin' down anyway.
My son, bless him, spent most of the afternoon in the port locker, while I guided the hose through under the head and in the lazarette. The hardest part was redoing the wire ties under the head counter to hold the hose up before it turned down into the muffler. The new hose is much more supple than the old one, so makes bends much more easily.
The old hose didn't have any particular holes in it, just cracks all along its length. I'm sure it was leaking big time for many years, based on the black soot all over everything. Having Morgan on his back cleaned up the port locker pretty well!

We have a bunch of lines in the lazarette, so I was able to avoid stepping on the cockpit scupper drains and the bilge pump hoses.
I'm glad I removed the aft cabin panel - I was able to guide the hose down and past the fuel tank, otherwise it would have been more difficult to figure out what was going on down there from up above, and you simply can't reach from the head door over to port to grab the hose from the head.
Thanks a lot for all the guidance.
Elapsed time, including removing and replacing all the stuff from the port locker: started at 12:30, finished at a bit past 3:30. Doesn't include time I spent earlier removing the hose clamps at either end and taking off the aft cabin panel, say maybe and hour.
Good help is hard to find, all ya have to do is put them through college!

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[added Nov. 2020] --- One thing I may have mentioned elsewhere (or not?!?): Where I bought my hose, they didn't have a full piece of 17 feet, so the helpful counter-guy Mark - who knew me - at the Universal dealership in Oakland, California (relatively 2014? newly renamed Outboard Motor-shop from Seapower) actually spliced two pieces together to make 17 feet with a high temp butt connector! I added two hose clamps on either side, but it was a tight fitting, no air leaks. One piece was much longer than the other. We fed each end in from up above, through the port locker. The right side went into the hole down below just forward of the fuel tank, and the aft end went though the hole on the vertical bulkhead down to the thru hull below the transom. The butt connector couldn't feed through either of the holes, and it just so fortuitously turned out that the "bulkier" connector stopped right at the bulkhead inside the aft end of the port locker and made it all the way to the thru hull! I still maintain that it was great planning, not just luck! Raised hands
Morgan did get the new hose into new wire ties inside the port locker, but I never got around to completely securing it underneath the head countertop; can't even begin to reach it.
Good news? It should be a once-in-a-boatowner's life kinda effort. And God bless the next owner!
exhaust hose flix