Re: 150 Yamaha 3rd rebuild - help!!!
I leaning toward buying the parts from boats.net. The only problem is it will be hard to go into a local dealer and get the technical bulletins when I'm not buying parts. I am going to buy an oxygen sensor anyways but I need to make sure it was the problem. I tested it as per the Yamaha Manual. Pre test the volt meter said it was .003v. When put into the flame of the torch it jumped around depending how it was turned into the flame. The maximum was .856v. But turning it slighty it would drop to .432v. I have read in the forms that this is not the best way to test it but I can't perform the other test I found at "Bass and Walleye Boats" untill it is running.The artical called "Sevicing Yamaha's Super 'Sniffer'" by Bill Grannis it says "to test the sensor without dissasembling the cover , sensor and housing is to hook up a Yamaha test harness (part # YB-06767) or adapt a way to have a digital volt meter to attach to the gray and black wires to the oxygen sensor. Set the scale at 1-volt range. The other wires from the sensor are for the heating element and should be checked for proper resistance and voltage imput. Remove the front air silencer cover and run the engine until it comes up to temerature, at least 120 deg. before testing. The votage should show .3 and .6 volts DC for a good sensor and will vary continuously as the computer (ecu) adjust the mixture. A lower voltage reading indicates a leaner mix and a richer mixtures raises the votage output from the sensor. If the votage remains near 0.9 volts the oxygen sensor probe is showing signs of becoming fouled. While the engine is idling , carefully use your finger to cover the air bleed hole in the top of the cylinder throttle plate and watch for a significant change in voltage readings. By blocking the air bleed hole, that cylinder becomes very rich briefly as a result in reduced air flow, and the ECU should respond immediately to lean out the the fuel to air mixture. The votage should first increase because of the initial richer mix, then become lower as thew ECU leans out the fuel mixture to compensate. As you remove your finger from the hole in the throttle plate , the incresed air causes a momentary lean condition and the sensors votage output decreases in response. You should observe an increased volt reading as the ECU richens the fuel to stablize the engine. IF any of the changes in votage are very suggish or nonexistent, the oxygen sensor may be fouled and in need of cleaning or replacement." This is just part of the artical.It also shows basic operation and trouble shooting.I found this on the web, you should read the whole thing. I only buy two boating books DIY Marine Maint. and Bass and Walleye Boats. And I don't fish alot.
