470 I/0 overheat need help

[fazoff]

Hey guys I need some confirmation here with my setup. Mercruiser 470 running hot- the raw water inlet hose is in the front on the heat exchanger right? Took that off seems like pressure coming out and spitting water? Thermostat works fine I took that out and boiled it in water and it opens at 160- I was having a over heat problem only at 3500 rpm and above but not it will boil over at idle if I let it run long enough. Took the risers off also they look perfect no derby or
Clogging ? I'm thinking maybe a head gasket?

[spareparts]

Have you replaced the water pump impeller?

[fazoff]

No I haven't changed that this season- boats in the water now so I would have to take it out to replace it. I'm going to stick a hose in the raw water hose today and run it

[spareparts]

put a new raw waterpump in it, use a Mercury brand with a new upper housing, If any of the blades are missing, look in the rear of the heat excahnger for the missing pieces

[Cam]

Be sure to check your heat exchanger and if you have one, your oil cooler for blockages.