I have a 2000 90hp 2-stroke that overheated and will not start again. Compression is just below 70 in all 3 cylinders. Does this mean the engine is blown?

Background info that may be helpful: I was having an overheating alarm issue when going over 4000 rpms (the engine appeared to be peeing just fine with lots of water pressure). It had been about 2 years since the water pump was changed so I changed that along with the thermostat, pressure relief valve and temperature sensor. The alarm still went off when over 4000 rpms. I then pulled the exhaust and cylinder covers and found blockage and salt water corrosion inside the water ports. After cleaning thoroughly, replacing the gaskets, and running it, the alarm did not go off and it was running great during the 30 minute test run on the lake. I stopped about every 5-7 minutes and could put my hand on the sides of the engine (cowling off) and it was not hot at all. The pee water was the same temp as the lake water. Then running back to boat ramp it overheated, lost power and will not crank again. The engine was incredibly hot. Being cash-strapped, I am trying to decide my next move. Any and all help is greatly appreciated.