Bad Smoke at start up

[Tstone]

I have a '94 Yamaha 130HP with VRO. After it has set for a hour or more it smokes VERY badly when started. It still runs good, and after a while it clears out and quits smoking even at extended idle. I changed the old spark plugs and they looked fine. Any ideas?

[Operaman]

Most likely it is un-burned fuel at shut down. Once the excess fuel is burned at start up, smoke is mostly gone.
It is a 2 cycle thing. Nothing wrong with it, just happens. Consider it extra lubrication at start up.

[Tstone]

I appreciate the input, but when I say smoke, I mean as in a fog bank. While in the middle of the gulf the other day I anchored for a while and when I started the motor back up I had people coming from miles away thinking I was on fire. I've been around outboards all of my life and have never seen one smoke this bad. Could it be a check valve letting oil into the crankcase while the motor is at rest?

[jb123]

could be checkvalves or you have 2? hoses running to the airbox, 1 oil breather/overfill and 1 carb runoff.... sounds like your oiltank may be dumping into airbox....is the tank always at the norm level? do you tilt motor up before this happens?

[Lgmth]

that's the same problem I had. The engine oil tank pumped full and then into the air box covering the carbs. Started the engine and thought it was on fire. Was told by boats.net that it is a bad shut off switch in the tank.

[Tstone]

We have a winner!!! Thanks for the input. This has been an intermitten problem and it just so happens that every time I have looked at the oil tank it was at the correct level. Yesterday while I was on the water it started smoking agian. I immeadiately stopped the engine and pulled the cowl. Low and behold the oil tank was completely full and overflowing into the breather. Thanks for the help.