Hello all, this is a long overdue update - with the problem
solved (I think).
I got back to the boat in
Antigua a few weeks ago with a bag full of parts. Unfortunately the new
exhaust elbow was the wrong one! I ordered the correct one listed in the parts manual, and
Westerbeke shipped me that part number which was for an
elbow that looked right to me while at home but once on the boat I realized it was wrong. The output end was smaller than my original. Getting back in touch with
Westerbeke they figured out the right one, but it was, of course, back in the States. Nonetheless I installed the new wrong one temporarily filling the gap with scrap hose material for now. It held fine, but I was worried the smaller output would restrict flow and therefore not prove anything about other
repairs.
I also replaced the thermostat and completely flushed the
engine leaving the coolant side filled with fresh water only. I captured every drop that was flushed out and it was pretty darn clean. Just a small amount of grit came out.
With everything reassembled and filled I started her up and ran for over 30 minutes, plenty of that at high
RPM (2500) and in
gear (tied solidly to the dock, so a reasonable load.) The temp gauge settled at about 175 F, about 10 lower then my previously normal operating temp, with no sign of spiking higher. My IR thermometer read a steady 180 on top of the thermostat housing. Perfect.
I then installed a new temp sender but the gauge continued to show 175. So the old sender was just fine. I then drained the water one last time and put in a proper mix of coolant and water. Again the temp gauge settled at 175, and IR thermometer at 180. All I can conclude is the old thermostat was flaky, but I've never seen a thermostat fail with the sort of intermittent behavior I was experiencing. Maybe the original elbow was restricted after all, but it didn't seem to be. Perhaps it was something else causing my problem that all my other fiddling cleared out. No way to know for sure now.
I was alone as my wife still can't travel so I didn't get away from the dock for a true sea trial and load on the
engine, but I think my dock test was pretty good, especially since before all these
repairs the dock test showed me over-temp.
I have the correct size elbow now from Westerbeke and will install it on my next visit. Hopefully that will be the end of this saga and I'll have happy sailing and motoring days ahead.
Thanks for all input here.
JR