On Sun, 12 Aug 2007 08:20:15 -0400, "Roger Long"
wrote:

In 38 years around boats with auxilliary engines, I've never actually
experienced a clogged fuel filter so I'm curious what the first signs are,
at least for slow build up as opposed to the fuel line suddenly sucking up a
mess that's been kicking around in the bottom of the tank.

I would expect that slowly developing problems would first show up at
maximum RPM and fuel flow and that the engine would continue to run properly
for a time at lower power. If I make it a practice to bring my engine up to
full RPM at least once during every run, I should first see a failure to
reach the usual number, perhaps accompanied by some smoke due to the
injectors not getting enough fuel for the rack setting. Backing off to my
usual cruising fuel flow, which is about 60% of WOT, should give me plenty
of running time to get to a place where I can safely change the filter.

Next year, I'll put in a vacuum gauge but, in the meantime, will this
strategy work?

There are two circumstances where you get clogged fuel filters. One,
you are running dirty fuel and the filter is doing its job and
filtering out all the little bit and pieces that come down the line.
In this case the symptoms are a loss in power.

The second case is where you have a substantial amount of water/sludge
in the tank and that suddenly gets into the fuel inlet. In this case
the engine stops right now!

The first case is pretty common where you are using dirty fuel, we ran
into it constantly working in the jungle where we were refueling from
drums. The fuel we were buying was probably not very clean and
dragging the refueling hoses around on the ground certainly didn't
help any either. The equipment operator would come in for lunch
bitching that "the damned thing doesn't have any power" and we'd go
out and change the filter.

The second case is catastrophic in that the entire fuel system from
the tank through to the injectors will be full of water/sludge. You'll
have to bleed the tank and fuel line all the way to the injector pump
and then disconnect the injector lines and motor over the engine until
you get clean fuel that through the injector lines and (invocations
to the Engine Gods help at this point) connect the injectors and hope
that you can get it to light off.

If you are getting "dirty" fuel there isn't much you can do except try
filtering it before you pump it into the tanks. The second case can
*usually* be overcome by draining the tank sump before starting the
engines.


Bruce in Bangkok
(brucepaigeATgmailDOTcom)