We were recently asked to attend a vessel to investigate a Caterpillar C12 starboard engine with high coolant temperature.
The operator was rightly concerned and keen to get it resolved before it became a bigger problem.
(And he was also planning to get back out on the water the next day!)
When our engineer Cris arrived at the marina, he began his investigations by checking the contents of the seawater strainer. It contained a very small amount of weed, but nothing excessive.
He then removed the end cover of the seawater pump and confirmed that the pump impeller was in good order.
After using a borescope to investigate the saltwater side of the engine oil cooler and the main freshwater heat exchanger, it was determined that both coolers were in good order with no obvious blockages or restrictions.
With the main coolant system checks carried out, the coolant was drained down enough to remove the thermostat.
Cris brought the thermostat back to our workshop for testing, and sure enough, it was confirmed faulty.
We had these in stock, so along with two new thermostats (one of them will be kept as a spare on the boat) and the new gaskets, Cris returned to the vessel the same afternoon.
He fitted the new thermostat and ran the engine to help bleed any trapped air from the freshwater system, ready for a final test under load.
We have recommended that at the end of the season when the vessel is winterised it would be a good time to check the thermostat on the Port engine.
This was a great result for the vessel owner with the investigation, part sourcing, and rectification taking place on the same day.
The point here though is that there is now a spare thermostat on board which will be on hand immediately should the need to replace one arise.