2000 90hp Engine Blown?

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) I changed the water pump, thermostat, pressure relief valve and temperature sensor. The alarm still went off over 4000 rpms. I then pulled the exhaust and cylinder covers and found blockage and salt water corrosion inside the water ports. After cleaning thouroughly, 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.

Hi welcome.
Need the model or serial#
Profile?? Location??
If the comp is 70 on all 3 then you should try again with a different gauge.
You remove all the plugs to test?
Then try taking off the head and checking for damage.
Not sure if your 90 has a PRV (pressure relief valve)? If it does it needs to be cleaned or replaced yearly if it's in salt water.
Since it's been in salt, some of the bolts/nuts and screws can be a B to remove.Just take your time or you'll strip tread and break bolts.
The actual rebuild isin't that hard if you can find a shop to bore out the head.

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