Columbia County, Multnomah County and the Coast Guard searched McNary Lake on the northern end of Sauvie Island Friday afternoon for a missing kayaker.  The boat overturned in the water.  One man onboard was able to swim to shore but the other man was not.  A coast guard helicopter searched from the air, boats searched the water, and others hunted along the banks for the man.  Crews searched until it was dark but couldn't find the man.  Neither man was wearing a life jacket.  The kayaker's identity hasn't been released.