It just seems that running at this temp creates inefficient combustion chamber temps that results in carbon build up and much lowered fuel economy.
Not that !! much poorer efficiency and you save the weight and maint of an extra water pump, and heat exchanger.
About $1000 worth of parts for a car engine , worth it for most from new , seldom worth the hassle on a used boat.
If the engines are Sterling , Rolls Royce , Lycoming ,Allison or some other brand of classic or exotic it might be different.