White Smoke

[ChrisJackson]

I've got a 2004 25hp 2 stoke Yamaha. It was running down the river just fine at cruising speed when it just quit. I got a tow back to the trailer, and took it home. I took the carbs off, they looked brand new, spotless, not a hint of sand, dirt, varnish, etc.. Put them back on, threw a new set of plugs in it and took the motor to the river to test it. It started on the 3rd pull with the choke out. It smoked like I've never seen. It is coming out of the exhaust port. It would not idle more than a couple of seconds, but I could throttle up manually and at a mid-rpm level it would run for about 10 seconds then stop. I could restart by choking and pulling 3 or 4 times. Same thing. The smoke is very white and does not have a strong odor of burning gas/oil mix. It has just a little of that smell. The smoke isn't not hot enough or dissipate quick enough to be 100% steam.

I've owned this motor for a couple of years and it has never gotten hot and the water pump is strong. I do have the habit of running a 50:1 mix (instead of the 100:1 called for) through it every other tank or so, and it's never fouled the plugs.

I'm guessing that somehow the engine is getting water into the cylinders and that's whats making the smoke. I pulled the plugs and no water is visible, but that doesn't mean much.

There is no water leakage in the upper engine, everything looks perfect that can be seen. What should I do next? Thanks

 

[99yam40]

Re: White Smoke

Test all you can and then look at what you can not test
If compression, spark, and timing are all tested and good then you are left with fuel/air mix problems
If no signs of water on plugs I would not look too hard at that
Check fuel pump and lines
condition of fuel
Carbs have to be adjusted properly after cleaning and reinstalling every time , follow steps in service manual
If you have to choke it I would look into cleaning carbs jets/ passages properly , not just looking in them and reinstalling

 

[James R]

Re: White Smoke

The old spark plugs depending on how old they are, should have had some dark deposits showing. If very clean then you could be getting water into the cylinders. Use a pen light and look into the bores. If the pistons look clean you could be getting water into the cylinders.