Hard to discern from what you wrote if it is both engines you are worried about or only one.
200f is not overheating. 210f is considered the top limit and your alarm should start at 215f. Any engine protection you may have (murphy etc..) should shut you down at 225-230f.
When I trouble shoot these problems, on one engine, the first thing I do is verify the temperature with an independent test gauge that I usually, if room permits, install in place of the temp sender. That way, I know EXACTLY what I'm dealing with and won't chase a ghost or my tail because of a bad sender. Your methods may vary, as they say.
A couple of common problems that cause overheat, especially after a service are;
Too much antifreeze in a closed system. Undiluted anti-freeze does not conduct heat very well. So, a mixture of over 50%/50% coolant to water will raise engine temps in hot conditions. Even in freezing conditions, 65% coolant is the max that should be used because pure antifreeze will actually freeze. Many people, including mechanics I've worked with, don't know this and I've seen 100% antifreeze used many times. If a little is good, then a whole bunch is better...right?
If the seals in the thermostat housing were installed incorrectly or not replaced at all, that will cause precisely what you describe. The seals are fairly critical in directing all the coolant to the heat exchanger when the thermostats are fully open. if the seals allow coolant to flow through the by-bass at all times, the maximum amount of cooling can never be achieved. In fact, over heated coolant will be flowing directly back into the cylinder head at maximum engine load demands and will accelerate overheating.
Then, there is the 1/3-1/3-1/3 rule about removing heat from an engine. The cooling system usually only removes 1/3 of the heat from the fire you are using to propel your vessel. Another 1/3 needs to exit the engine through the exhaust and another 1/3 is basically radiated into your engine space from the engine surfaces. I tell you this because a plugged exhaust or a very dirty engine will cause high coolant temps.
hthy
jimmyd