Idle and smoke problem

[atzitz]

I recently started having problems with my 4 stroke 4hp Yamaha outboard on my small sailing boat. It took me quite some time to start it the first time after the winter break and once it was running I had to keep the throttle at high spead or else it would die. After trying to leave it at idle at low gas many times I gave up and went doing some other after-winter stuff. After about 10 minutes I tried again. This time it started immediately but straight after there was an explosion-like sound and a small cloud of white smoke got out under the engine hood. But to my surprise after this the engine ran like new - no problems with idle any more.
I went out sailing for an hour or so and when I tried to start the engine again (after it was tilted and rocked by the waves for a while) there was another explosion-like event, this time stronger and with much more smoke and some oil/gas (I am not sure how to tell between the two) drops appearing on the water. In addition, the idle problem was back again.

any ideas what's the problem and what should I do?

 

[Silvertip]

Re: Idle and smoke problem

How was the engine winterized? Fuel system treated? Was the engine removed from the boat perhaps and stored on the wrong side which allows oil to get into places it is not supposed to be?

 

[robert graham]

Re: Idle and smoke problem

Maybe when you tilt motor up for a while fuel is leaking out of carb into combustion chamber, then when you start it up you have a rich fuel mixture event(boom/smoke), backfire through air intake. Before you turn motor off, shut off fuel supply to allow fuel in carb float chamber to burn down and become lower level, hopefully that may help. Always turn fuel petcock off when motor is not running to keep fuel from leaking past carb float into motor. Good Luck!

 

[atzitz]

Re: Idle and smoke problem

Thanks for your answers.

I didn't do much before the winter. Simply tilted the engine in its place so it was outside of the water and closed the fuel valve.

I'll go tomorrow to the boat and try to find any signs of possible leakage and let you know if I come up with something.

Thanks again.