The ratings given are based based on the total output power of the engine and reflect a seawater inlet temperature of 32°C as prescribed by  classification societies i.e. Germanischer Lloyd.

Important:
The heatexchanger should be mounted with the header above cylinder head  level and with the engine water circuit arranged so that it is self venting on initial filling. A by-pass type thermostat should be used and arranged so that only the heatexchanger is by-passed when the engine is cold. All other components including a water jacketed exhaust manifold if fitted, any oil  coolers, charge air coolers and exhaust gas heatexchangers should be so  positioned in the circuit that they always receive the full flow of the engine  water pump. Thermostats of the type used on some automotive engines, which  simply interrupt the cooling water flow when the engine is cold, are not  recommended.
For unattended operation, automatic engine shut down equipment should be provided.