It's to foggy to see across my back yard this AM, so I'm working
instead of cruising to Poulsbo for lunch. :-(

The brief guts of something I'm preparing....

Larry Stewart, of Stewart's Marine in Seattle, tossed me a little metal
engine fitting last week and asked, "Why don't any of you guys ever
write about this? We just took that off an older Chris Craft, but there
are thousands of boats around with the exact same situation. We caught
this one before anything too drastic happened, but you wouldn't want to
see what's left of one poor guy up in Alaska. The same part failed on
his engine, he was aboard, and the explosion and fire burned him so
badly he might not consider himself all that lucky to be alive. I was
called as an expert witness when he sued the engine manufacturer. Ever
since, our guys are instructed to check this part on any engine where
its fitted any time we service one. Once the conditions are in place
for a failure, it can happen pretty fast."

I examined the part. It was essentially a metal cup, about three inches
deep and two and one-half inches in diameter. There were threads just
below the open end, and a flange around the lip that would suggest the
part should mate up with another component.

"That's a metal fuel filter canister," said Larry. "The filter itself
is paper and can be replaced. Look into the bottom of that part and
tell me what you see."

At the bottom of the cup, concentrated in an area immediately to one
side of the lowest point on the concave surface, were scores of little
"craters". Something had been pitting and corroding the metal. When
held up to the light, it was immediately evident that the fitting had
failed entirely. There were two "pinholes" of daylight, and if the
canister had been in service on an engine, fuel would have been
spilling into the bilge through the openings.

"It looks like it corroded through."

"Exactly," said Larry. "When anything is grounded to the engine block,
all the metal parts on the engine actually become part of a circuit.
Junk gets filtered out of the fuel, and settles in the bottom of this
filter bowl. If there is any sort of metallic content in the debris, it
will react with the dissimilar metal of the filter bowl through the
liquid medium of the fuel. This corrosion is the result of junk
accumlating in the bowl. Anybody changing the fuel filter needs to
remember to clean out the bowl, and check for these little craters. It
doesn't take all that long
to corrode right through one of these filter canisters. If people see
any sign of pitting or corrosion it makes sense to replace the bowl."

Larry has an excellent point. If an engine is fitted with a "spin on"
fuel filter, the canister is discarded when the filter is changed and
any accumlated debris will be tossed out as well. When changing fuel
filters that use replaceable paper elements contained in a "permanent"
metal housing, a boater should remember that simply swapping out the
paper element doesn't constitute a complete service. Cleaning out the
bowl and inspecting for any evidence of corrosive pitting are critical
steps when an engine is fitted with a metal fuel filter housing.