Via the service manual, the compression test should be 176 PSI, so you're low in that regards at 150 PSI.
You may very well have a bad head gasket.
Also, what kind of water was he using? Tap water (I hope not), distilled, or better?
If he was using tap water, the radiators could also be full of mineral deposits which could also affect effective cooling. If so, you might need to flush the system with chemical solution to dissolve the minerals.
I hope no water got down into your oil. Is it creamy looking and frothy?
I love how the previous owner band-aided the problem instead of fixing it.