80C or 176 is the normal operating temperature and if the cooling system is working correctly, the temperature should not increase more than 5-8% even at the highest RPM. When you measure 80C on the oil filter, you should measure 50C at the exhaust elbow immediately after the water inlet to the elbow. If it is higher, there is a problem that may be one of the following.
Possible Causes of Overheating:
1. Restricted seawater flow anywhere in the pathway beginning with the seawater entry into the sea chest to the seawater and exhaust exit through the hull.
2. Restricted Coolant water flow
3. Incorrect coolant ratio, but this is usually not a major contributor but will contribute somewhat.
4. Incorrect V-Belt tensioning with the V-Belt turning the coolant water pump
5. Failing Coolant Thermostat (not opening completely)
6. Other engine issues
Do not think that you can measure enough water flow by observing the seawater and exhaust exiting the boat. It will fool you.
On Thu, Sep 2, 2021 at 1:40 PM Jose Venegas via groups.io <email@example.com> wrote: