"Clams Canino" wrote in message
news

I 've repaired *many* Mercury outboards that were designed for a 50/1
pre-mix - that somehow got put on a sudden wayward diet of straight
gasoline. Damage and results vary. This is probably dependant on
operating
RPM and residual fuel mix left in the old tank.



Clams,

Your posts are normally knowledgeable and informative.

I can't comment on Merc ouboards run without oil, but on Johnson-Evinrudes
they will idle for hours with no oil in the gas. But when you accelerate
them and run at or close to full speed, the big-end rod bearings start to
smear which takes out the crankshaft and rods, plus the cylinders score
deeply and the wrist pins turn blue, as well as the main bearings. The
ball-bearing bottom main lasts the longest as all the fuel "drippings"
accumulate there.

Small motors will normally quit very quickly when things start to freeze up,
but higher hp engines will keep running longer as there is more power to
keep the damaged parts turning until catastrophic failure occurs. Computer
controlled motors are the same way, as the motor loses power, the computer
adds fuel and spark trying to keep the power up, thus bootstrapping the
damage.

The main point I was making for the "VRO" question was that ALL the
cylinders, pistons, and bearings would be damaged from lack of oil, not just
one.

Bill Grannis
service manager