I have a 1994, 70 HP Johnson outboard. When I first start the motor I get a warning sound that indicates either the motor is not getting oil or it is overheating. The engine is definitely getting oil as there is lots of smoke coming out of the exhaust. To me it is not overheating as the water coming out of the cooling system on the side of the motor is not overly hot. (feels normal temperature) I have been told that it could be the heat sensor may have failed giving me a false warning. Is this common problem? Any suggestions would be helpful. Thanks.