How hot is too hot?

Tony, from what I've read the FWC motors run a little bit hotter then their RWC counterparts. I've found running temps for both motors, but have had no luck finding the "too hot" temp. Perhaps when the experts chime in they can get us a too hot number for both FWC and RWC motors.

Also, (not to thread jack): I was thinking of documenting different temps in relation to what it says on the gauge.

Ex.:
Condition = Post warm-up idle
Gauge Temp = 160
IR reading @ temp sensor = 140
IR reading @ circulator pump = 143
IR Reading @ top or right riser = 100
IR reading @ top of left riser = 101

Condition = Post barefoot, idling to cool down
Gauge temp = 180-200 (guessing between lines)
IR reading @ temp sensor = 165
IR reading @ circulator pump = 125
IR Reading @ top or right riser = 125
IR reading @ top of left riser = 123

I've noticed that at some of my highest gauge temps, the circulator pump readings are considerably cooler. I attribute this to a properly working thermostat, it's opened up allowing lake water to cool the motor. The temp sensor just happens to be at the highest spot so it's seeing the hottest water after its been though the block.

i'm not a FWC expert but i would think a constant 180 is ok but dips down to 160 indicate something isn't right.

if the engine has the ability to run 160 then i'd only expect to see 180 on a long hard run

You are forgetting a FWC system is pressurized just like a car or truck. Why? it's to keep the coolant from boiling over 212 (sea level)! What temp is your car running at!

Several things to look at when running hot
water flow is number one and it can be water pump and or exhaust risers and elbows.
Heat exchangers can have a build up of scale inside the water jacket side that can also prevent efficient heat transfer.
too lean a/f mixture can also raise temp.

I would pull risers and elbows and acid wash in pool acid, will remove bulk of the rust that may be clogging the water flow.

Would next pull heat exchanger and also acid wash it.   would use vinegar and let it soak for a few hours in it. less aggressive than pool acid.   will not damage the thin brass.   

Would also look at raw water pump. Is wear plate in good shape? is back of housing in good shape, impeller etc.   

Lastly yours will have transmission cooler but it may not have oil cooler. I recommend oil coolers.   

My Crusader 454's in my big boat never ran hot, i maintained the cooling system as described and also it had both transmission and oil cooler..

Inspect spark plugs for proper combustion a/f mixture.

I didnt use the boat much last season so i dont recall it getting too hot. I did notice a crack in the strainer cover so i ordered a new one today, that should be her tomorrow. and i have some new wire reinforced coolant hoses coming to replace a few that look like they might be restricting flow.
I'll report back if it makes any difference but for the meantime 200* is acceptable to me. so i guess any improvement will be an extra improvement.