The cooling system seals on an engine are only designed for 13-15 psi or so. Putting 50-60 psi in an engine is stupid. It may hold on some engines, but there is no reason to raise the boiling point that high. A proper cooling system needs a restriction on the outlet (valve or an orifice in t-stat housing) to raise the pressure above 0 to raise the boiling point over 212F and to help keep steam pockets from forming.

If you really want to control the temp correctly a closed system with a heat exchanger would be a better idea.

Keeping an engine too cool will reduce combustion chamber temp. You want heat in the combustion chamber to make power. Tuning also changes with temp so a boat that has an engine that does not fluctuate temperature will be easier to keep in tune.

There is a reason the average car runs between 210-220F. It's more efficient and you end up with a cleaner burn than if the engine is at 150F.



You want pressure in the block to raise the boiling point, even though the engine will mostly run at a set temp, some parts of it will be warmer and cooler than wherever your sending unit it. That means some spots could get over 212F (boiling point at one bar) and create a steam pocket. Once that steam pocket is created there will be no cooling at that location until it is removed.

Keeping an engine too cool will reduce combustion chamber temp. You want heat in the combustion chamber to make power. Tuning also changes with temp so a boat that has an engine that does not fluctuate temperature will be easier to keep in tune.

There is a reason the average car runs between 210-220F. It's more efficient and you end up with a cleaner burn than if the engine is at 150F.

You want pressure in the block to raise the boiling point, even though the engine will mostly run at a set temp, some parts of it will be warmer and cooler than wherever your sending unit it. That means some spots could get over 212F (boiling point at one bar) and create a steam pocket. Once that steam pocket is created there will be no cooling at that location until it is removed.

Is the water allowed to stay in the system long enough to even reach a "warm" temperature? Or should it be?

Block pressure will vary depending on: where the gauge is installed in relation to the dump line
                                                         what size dump line and how many of them
                                                         what is the dump line fitting outlet size
                                                         head gasket design I.E. car or marine
                                                         water feed line and "T" size
                                                         max engine RPM/HP (higher RPM means more bowl pressure)
                                                         nozzle size (changes bowl pressure)                 
                                                         bowl and impeller type (see above)
                                                         BB Chevys depend upon the year of the block, I.E. 1,2,or 3 center/lower coolant deck holes and     
                                                              Gen 4,5,or 6, they have different front and rear deck holes
                                                                        TIMINATOR

GT I disagree.
You all figure it out since I don't like to restrict the flow anyway.
The abovementioned info was a result of over 40 years of being both a performance machine shop owner/operator specializing in boat engines AND pump builder/ machinist.   
Others experiences may vary.   
TIMINATOR