OP here, an update;
If at all possible I woulds prefer to buy the correct replacement. I took a look at the supplier listed in the first page of this thread, sadly to ship to Canada they require a money(wire) order. Seriously? I could start a rant on USA based companies who make it difficult to ship to Canada
Via google I found another company that sells what I am looking for and am waiting to here back from them.
John, since you have a lathe, why not build up 3-4mms of a good filled epoxy on the tube, then turn it down to 1-3/4" so the two match? Epoxy is a structural material, after all. Easier than turing Delrin blocks and fussing with all that.
Or, of course, just buying the new one in the right size.
Your last sentence says it all, for <> 100 $ I prefer to buy rather than make. My lathe turning skills are limited, with that said if I need to I will use it for this situation, as you discribe.
I suspect I could just buy 1 3/4 hose, clamp it all down and be done with it. It worked for the first 30 years....
With that said the boat is out for the season so why not take the time to do it right and the forget about it for the next couple of decades?
Thanks for all of the feedback,