Thanks for the ideas! This turned out to be a fairly deep rabbit hole, with a happy ending.
I started off thinking that it was a bad
sensor or other
electrical problem, because I did not see signs of actual
overheating. The temp gauge stayed in the normal range and IR readings were reasonable, maybe a bit high depending on the exact location tested, but nothing obviously screaming "I am over heating!" That all changed when I disconnected the over temperature switch sensor. The generator started and ran normally for 15 minutes or so and then overheated for real.
Coolant tank cap venting, boiling coolant in the overflow bottle, etc. I should have caught it sooner, but I wasn't watching as closely as I should have. Hopefully no harm done other than losing some coolant.
Running 10 minutes or so and then
overheating now sounded like a bad thermostat to me and low-and-behold I have a spare thermostat in my box of generator
parts.
To get at my generator for this kind of surgery I need to empty a cabinet and then disassemble it. This was a b*tch because there's no freakin'
wind here and it's hot as hell. I get part way into the job and realize that it isn't possible to change the thermostat without removing the coolant tank/exhaust manifold and
heat exchanger.
A few curses later and those
parts are unbolted, but I can't get the exhaust hose off the mixing tube. I finally unbolt the mixing tube from the heavy cast iron manifold/tank and the
bronze HX and leave it there on the end of the exhaust hose. With the manifold and HX removed I can at least
work up on
deck and it takes me no time at all to remove the cover for the T-stat and remove the T-stat. Oh crap! That thermostat does not look like the new one in my hand, what is going on?!
Turns out the new T-stat is for my main
engine and got into the wrong box. I have no new T-stat for the generator, but maybe this one works? I clean some RTV and scale off and put it in a pan of
water on the
stove. 160F later it opens right up! I clean a bunch of rust and scale out of the manifold and HX and re-install everything. I fill with coolant and start her up for a test. It seems to be going well, but wait, where is that
water coming from?? Oh no! The exhaust hose has sprung a leak! I shut it down and examine the hose to discover that it's old and rotten where it connects onto the mixing tube.
I borrow some silicone "rescue tape" from a neighboring
boat, but I can't use it because the exhaust hose is pressed against the side of the generator making wrapping tape around it impossible. Next, I cut the bad end off the hose and attempt to reattach it. There isn't really enough slack in the hose now that it is a few inches shorter, but I manage to get it partway onto the mixing tube and clamp it down with a hose clamp. Start it up and water everywhere!
All the pushing and pulling on the old brittle hose has opened up multiple
leaks and it is now obvious that the entire length of hose must be replaced. It's late in the day and I give up and go to dinner on shore. Dinner is good but I don't sleep well thinking about how unlikely it will be to find the hose I need here on San Cristobal.
The next morning I awake with new vigor, remove the old hose and
head into town where there is a
chandlery. Okay, not really a
chandlery more of a
hardware store, but they do have some
boat parts. The man at the counter looks at my old hose and disappears into the back. He returns with nothing but says there is "a guy who fixes buses" down the road who may have it. I get vague directions in Spanish (which I don't speak) but they are good enough to find the bus garage. The man there takes one look at my old hose and says, "no way." Then he says there is another guy further down the road, take a left and then a right and then ?? who might have it. I've got nothing to lose at this point so I
head down the road. I take a left and then a right and seem to be heading out of town. I'm just starting to ponder how far I should walk before giving up when a small truck pulls along side me. The driver looks at the old hose in my hand and says, "maybe". He gestures to me to get into the truck and off we go. He drives clear across town and stops at a dirt lot with a chain fence surrounding a warehouse type building. He unlocks the fence and then opens the roll up door to a garage full of old boat parts! He starts digging in a pile of junk and throws out one hose after another, no, no, no, all the wrong size. Then he says "ah!" and pulls out a beautiful section of 2"
marine exhaust hose!
We jump back into his truck and he drives me back to the
dock. Here I pull out my cash and try to pay him but he refuses. I try again but he'll take nothing, he won't even let buy him a
beer. Back at the boat I install the new hose and now the genset runs great! Thank you Marco!!!!
What a difference a day can make! Yesterday, my
batteries were very low, my water
tanks almost empty, and my generator was broken. Today, full batts, full
tanks, working genset! Life is good again!
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