Overheating Yamaha 1986 V6 150 2 stroke

Can anyone tell me the direction cooling water passes through my outboard? It overheats in a couple of minutes, and I see no water reaching either thermostat (cover removed), but the outer exhaust jacket is full of water and the tell-tail has a good stream. I am looking for a blockage. Is the exhaust cooling closest to the impeller, or furthest? Many thanks.

[boats.net]

If you haven't replaced water pump then replace it, check pressure control valve to see if stuck open. Next step would be to remove heads and clean water jackets.