Tohatsu 25hp 4-stroke overheatingpipes salting up

I have a 3-year old regularly serviced 25hp Tohatsu outboard bought new. Despite ALWAYS flushing out in fresh-water, the engine is getting hot, but no warning sirens or lights to indicate a fault and its only the tell-tale water temperature that indicates something is wrong. No 'limp mode', nothing. In fact the engine runs exceedingly well. When taken back to dealer, he confirmed thermostat working but replaced in case, impeller changed etc etc, but now he has said the pipes were completely blocked with salt. (yet water still running freely through them?). I can only assume that the engine is running so hot that when engine turned off the water evaporates so quickly that salt is left behind, although this should have cleared through flushing process. Has anyone else come across this problem?

Try an infrared laser gun to pinpoint problem area. Can you keep your hand in telltale stream indefinitely,if yes motor is fine. Run motor in vinegar solution to eat away salt inside of engine. Another test can you place finger on cylinder head for a six second count before burning it?

The MFS25/30 has a computer connector. That allows a technician with a laptop to see the actual temperatures. What number did the dealer see? Failing that, you can use an IR thermometer as Johnny suggested. Case temps should be in the 150F range.