Running Hot
Recently my Volvo Penta engine, based on a 350 Chevy, started running hot. The thermostat needle which normally swings in the yellow and low end of the green (normal) band, was moving in the upper end of the green band, dangerously close to the red band. Now as you likely realize, this is typically a good point to secure the services of your local professional. However, if you feel comfortable with the possibility of sinking your own boat, as I did, you might move ahead and reflect on the many components of a raw water marine cooling system: hoses, filters, pumps, thermostats, sensors, etc.
With all this stuff, it can be a bit difficult to accurately diagnose a cooling problem quickly and I found that the best idea is to move slowly, logically and methodically. I determined that I had good water flow coming out of the water pump, so I knew the system was working up to that point. My suspicions turned to the adjacent thermostat, so I ordered and subsequently installed a new one. Much to my chagrin, the new thermostat did not solve the problem and the engine continued to run hot.
So, I bought an OEM thermostat kit and a couple extra gaskets. I took the system apart again, installed the new thermostat and bolted everything together. I started the engine and, just to satisfy my curiosity took a look at the thermostat housing, where I could see salt water spraying from the back. I took everything apart and reseated the gasket and put it back together, and started the engine again. Still, the leak continued. Then, I disassembled everything and put one of the extra gaskets in, and this time the engine started and ran leak free. And, the new thermostat operated as promised.
Lessons learned. One, know you limits, be careful not to try to fix things that are beyond your abilities. Two, take it slow and stay focused – the boat you save may be your own. Three, consider using OEM parts to ensure proper fit and function. Four, buy some spare pieces if you can. And finally, check your work to avoid serious problems from arising unexpectedly.
