Yamaha F100 AET smoking

[brunsgaard]

Hi,<br />I have a '99/00 F100 and it runs great, but this season it has started to (occasionally) belch blue smoke out of the hole on the back of the engine (above the waterline -not through exhaust/prop). It happens after having drifted for 15-20 minutes w. engine off and then when I start it again. The smoke smells of burnt oil. The engine probably has a total of max 300 hours on it, had its last oil-and filterchange in April last year (meaning 20 running hours ago). I did not use original Yamaha oil, but bought a cheaper oil, but with the required specs. <br />I have read through all threads on the topic and seem to find some correlation between angle of tilt (I assume when planing ?) and subsequent start of engine.<br />1) Why is this and why does it start happening now after more seasons of usage ?<br />2) Does it mean anything ? should I change back to original high quality oil ?<br />3) I hate the smell of burnt oil - brings back memories of poor-quality eastern cars. Could the piston rings be worn already ?<br />4) Does Yamaha publics tech bulletins ? If so, where ?<br /><br />Any help is appreciated<br /><br />best regards,<br /><br />Poul, Denmark

 

[Propnuts]

Re: Yamaha F100 AET smoking

If you look at the position of the engine when tilted down all the way, the cylinders are on a horizontal plane unlike a car engine were they are vertical plane. If the engine is trimmed down all the way the spark plug end or top of the cylinders are actually below the back end of the cylinders. <br />You shut the engine off in the trimmed down position and there will be engine oil that will pool behind the pistons depending on there position and over a period of time the oil will seep by the pistons and rings and get into the combustion chamber. When you start the engine the oil burns hence the blue smoke. It usually will go away pretty quick.<br /><br />To get rid of this, just trim the engine up a little when it is not running. This way the oil will go back to the oil pan where it belongs.<br /><br />Try it........

 

[brunsgaard]

Re: Yamaha F100 AET smoking

Thanks, Propnuts I will. When stopping it is normally after having sailed (planing) for a while where the engine would be trimmed slightly "out" meaning the plugs slightly higher than the pistons though, but I will give your advice a try though.