Engine problem again at night...

Just as we got ready for the night, trying to catch some sleep that we missed the previous night, the engine started giving alarm of very high temperature. We stopped the engine immediately, put up sails and again started opening the engine at 10pm. Engine was extremely hot and we decided to check the sea water cooling system. The pipes had cold water all the way to impeller and very hot water after impeller, indicating that the impeller was no doing its job. This time we took it apart much faster given our experience from previous night. The impeller looked okay, but was not turning freely. After fixing this we turned the engine on and it worked fine... We retired to our shifts: Mick 11pm-2am, Anil 2am-5am, Murat 5am-8am.
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