oil leak-phantom

Hi everyone!

i have a 2000 yam f9.9 mshy four stroke. Im experiencing an oil leak that even professionals cant find. Dye has been put into the oil to be seen under a black light.

Heres what happens. I can have the motor working hard in the water constantly running for 2 days and then I will find oil on the 3rd day in the motor housing and in the water. This has happened on 2 different occasions and the motor is on the transom. I have lost up to 1/2 a litre of oil. At one point when I fired up the motor cold white smoke came out

I have mimicked this also in the back yard in a test tank. It almost seems that its caused by expansion and contraction of the aluminum at a gasket somewhere in the motor.

Will bolts lossen after a while ? Any Ideas? Any other way of problem solving this scenario ANy help would be greatly appreciated

[boats.net]

It's hard to say. A oil leak on exterior of block wouldn't cause it to smoke on start, that could be valve guide seal. Has the mechanic done a compession and cylinder leak down test?

oil leak

Thanks for the reply!

No I dont believe that they did a compression test. I have spent $300.00 with no avail.

I have been running it in a test tank I have made and have been running it every day with no visible leaking a little bit of pooling of oil yes in the base of the cowling. I have washed out the interior of the cowling to look for new pooling.

No white smoke since.

I have been putting the black light to it nightly and trace oil pooling is evident. I have even taken a infrared thermal camera to it on two occasions. I Have reviewed the first set of thermal images with nothing showing of interest.

[boats.net]

You can use a aerosol spray powder like foot powder to help find oil leaks. The block has to be clean and degrease then spray powder on suspected area and then watch for wet spots.