Ouch! To bad!

Just to do a preliminary test, draw a sample from the fuel line so you
getting the same fuel your engine was getting. You could do this by
disconnectin the fuel pump discharge line and operating the hand priming
lever.

Put it in a clear glass jar and then go get some marine diesel a the fuel
dock and compare the two.. You should be able to tell from the color, if it
was deluted to 50/50. Of course the marine diesel should have a purple
color.. If you got the fuel at a highway gas station, the the diesel will be
almost clear in color..

If your still not sure, then pour a little out into an open pie tin and toss
a match in to it. If it flashes right up, then it's most likely it has gas
in it.. The straight diesel will just burn like kerosene (may even put the
match out).

If you ran your engine for even 8-10 min even with straight diesel at 280,
you are in trouble. It's a wonder it didn't seize. If she kept oil pressure,
the bearings may be ok but your cylinders may be scored. The fact that you
estimate a 50/50 mixture, may be enough to have saved them.. However if your
able to establish the liability of the fuel dock, then your fuel injector
pump and injectors will need to be tested by a shop and rebuilt or
replaced..

Good luck and hope for the best.

Steve
s/v Good Intentions