Went fishing last weekend.  After the first run, my wife says, "What's the oil sheen on the water from?"  

It turns out the filler cap for the hydraulic fluid on my power trim unit somehow worked itself loose.  I lost pretty much all the fluid - replaced by lake water.  

The good news is that it's covered under Yamaha's warranty, so I get a brand new trim unit.  The bad news is that it's in the shop until next week, so I'm land-locked when the fish are biting!!  AAAGH!!

I'm curious, though, has this happened to anyone else?  It seems really out of left field to me. I've never known this to happen before, and I've been fishing for decades.  Thoughts?

Not that problem but my Yammie, along with many others had a problem with the oil ECU.  It would fail to detect the OB oil reservoir was full and would continue to pump oil into the OB reservoir until it popped the top off and then began dumping oil intp the inside of the ob which eventually made it's way into the lake.  I remember fishing one day, looking back and seeing an oil slick down the entire bank I had just fished.   ;D

Pulled the cowling and found the problem. $180 for the ECU seemed kinda steep though.