Overheating and RPM

Hi guys greetings from Greece.

Hi guys greetings from Greece.
Recently I became the owner of a 12 meter Trojan Express model 89 with DD 671 J&T 450 HP. When I bought the boat the engines had 850 working hours. From the beginning the temperature of the starboard engine was about 15 degrees Fahrenheit higher than the temperature of the port engine. Lately when I am cruising at 2.100 RPM the temperature rises to 185 degrees Fahrenheit and if I press harder 2.200 RPM it rises even more. I’ve noticed that cooling water is coming out from the expansion tank.
Any ideas what I should look for? Please also let me know which is the appropriate RPM to run the engines. The constructor says 2.200 but they seem a lot to me.
Thank you in advance for your replies.
Sotiris

"my 453 does this, i looked at

"my 453 does this, i looked at the cooler cores and found a lot of rubbish in the tubes, you really need to start at the pickup and work your way forward. if you make sure everything is clear and clean i think you will fix your problem. a compression leak is possible but i would think the coolant loss is due to the higher running temp unless it is excessive."

Thanks for your suggestions.I

Thanks for your suggestions.I have planned to clean up all the coolers this winter.Also i have another question what is the difference between paraflu and nalcool because that stuff does not exist in Greece