470 I/0 overheat need help

fazoff · #1 10-12-2015, 05:35 PM

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 · #2 10-12-2015, 07:49 PM

Have you replaced the water pump impeller?

fazoff · #3 10-13-2015, 09:16 AM

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 · #4 10-13-2015, 08:51 PM

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 · #5 10-14-2015, 05:57 AM

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