View Full Version : Yamaha 250 cooling probleam

03-13-2004, 01:13 AM
" ihave 1999 yamaha 250HP two engines.

in one of the engines, the water cooling is weeak and the I replaced the impeller and the two gaskets on impeller housing (thin one on impeller housing to steal plate-down and the top one for pipe)

But the water force is still weak and engine heats up.

Where should I look further?

the ingines are in good shape.

Any ideas will be of help "

03-13-2004, 01:43 AM
If you have done the waterpump job properly I would be looking at the pressure relief valve.
This valve remains closed so the block can fill up with water. If this is stuck open the water would drain and not allow the pump to build up sufficient pressure in the block. You will find this valve at the back on the exhaust cover. It may also pay to check the thermostat/s while your there.

03-13-2004, 07:32 AM
Blown head gasket will lead to overheating.The poppit valve opens when the motor is at higher speeds to allow more water to circulate. At idle the thermostat looks after controlling engine temperature.

03-14-2004, 12:04 AM
" I checked the thermostat, and both thermostat are missing in both engines however only one engine is heating, actually, the engine that heats DOES NOT pee properly. "