Way back in January, as we left Tenticatita Bay for a day sail (aka dumping the heads out at sea) with Aunt Stephanie and Uncle John aboard, I noticed that our Yanmar temperature gauge was reading very high before the engine even reached normal operating temperature. We watch the temp gauge like a hawk since experiencing two cooling system blockages over the years. We immediately reduced RPMs and limped back to the anchorage to investigate.

John and I did some temperature checks with a digital thermometer on the thermostat housing and found that the temps were ok and suspected either the sender or the gauge. Later on, thanks to some long-distance troubleshooting with Shawn Wurzner, we confirmed the gauge was fine, so I went to the spares kit only to discover that my Yanmar temp sender was not the correct one. Hunter had replaced it with their own to maintain compatibility with the Hunter (not standard Yanmar) instrument panel.

We ordered the right sender from Hunter and scheduled maintenance here in La Cruz. And since we were opening up the fresh-water system, we might as well clean out the heat exchanger, which was previously causing overheating at high RPMs. If were bashing home, we may need 3200 RPMs now and then. So we called Steve Mechanico and his son in to help out. Recall that Steve helped us replace our exhaust hose last January. And since were doing the heat exchanger and thermostat, we should probably change the trans fluid, do a full cooling system flush and repaint the trusty Yanmar where rust had started to form from various abuses over the years. Good thing we did, as we found a broken clamp, one leaky hose, another that was bulging, two that were chafed and a turbo coolant hose that was clearly fried. Par for the course for an engine with about 4000 hours on it. After 2 days we had a thoroughly serviced and shiny engine.

And them the moment of truth… I started up the engine and the temp gauge was still pegged! Doh! Oh well, we now know that the temps are stable and with a fresh heat exchanger and thermostat, odds are low that we will have a problem. So later that night I woke up t and remembered one thing Shawn recommended that I did not do. He suggested re-seating all the connections to the gauge and even running a wire from the gauge to the sensor to bypass any wiring issues. When we did our initial troubleshooting we thought we confirmed the gauge was working by grounding the sensor wire at the engine, pegging the gauge.

The first thing in the morning I popped the instrument cluster out and cleaned all the connections and reinstalled. I quickly turned the key and what do you know, the gauge was back at zero where it should be. I let the engine warm up and sure enough, the gauge works fine.

After years of cruising and many humbling episodes of Stupid Boat Tricks, I really thought I had cured myself of immediately jumping to the more complex troubleshooting steps rather than the simple things first. Apparently not.