have two yamaha 250 two stroke outboards (2007) with 320 hrsengines give temp alarm on higher rpmchanged impellers,oil,thermostatic valves,headgaskits,still same alarm on higher rpm,sdisplay shows only one line on the themperature display.
Hello my name is XXXXX XXXXX will help you with your problem. Your problem is either that you have some blockage in your cooling system or one of your sensors is not working correctly. So best thing to start with is to verify if the sensors are ok. The sensors are located on the top of the cylinder heads , one on each head. When the alarm goes high, disconnect these sensors one at a time and see which one switches the alarm off. That will be thew one triggering your alarm. Replace this sensor with the other and check again. If the alarm goes high again, check if it is the same sensor ( which is now located on the other head) which has triggered the alarm. If yes then it is the sensor. If it is on the same side which triggered then you have some blockage on that side.If on the other hand both engines are triggering the alarm them you might have the engines mounted high on the transom and it will pickup air while at high speed.If you need more information let me know.Noel
Advanced technical diploma
hi Noelwe where trying to disconect the temp.sensors on at the time than the other engine give also hightemp. alarmi was thinking it migt be a electrical fould.we opend up the poped valve on the back and also the big plate from the cooling jacket on the back of the engineeverything is clean and looks ok.the guy who is trying to fix the problem thinks there might be a blockage in water exhaust system.the pie hole has a strong streem of water coming out.regards XXXXX XXXXX de sande
Is the water hot? how high are the engines mounted? if they are mounted high, they will overheat when the boat is on plane since it will get air. Try covering the top 1cm of the pickup holes with adhesive tape and try run the boat again, see if it overheats. If yes then the engines are mounted high.Noel