Offshore with a single screw
From: Rudy and Jill Sechez rudysechez@yahoo.com
Subject: T&T: Offshore with
a single screw
To: Gregory Han hangreg@gmail.com
Hi Jim-
Greg has given
good advice. The most fun you will probably ever have is crossing the Gulf
Stream in a north wind; the fun is so overwhelming that you may give up
boating. Jill and I prefer not to have that much fun.
The clean tank idea is
more than a great idea. Based on my experience, with boats clogging their
filters, this means more than just polishing your fuel.
The only way to know
for sure if your tanks are clean is to open them up and visually inspect them,
particularly the bottoms, and in each compartment.
I have dealt with many,
many tanks where the crew has had their fuel polished, not just once, but
several times and still had troubles. Once the tanks were emptied and
inspected, there was always contaminant on the bottom, from a fraction of an
inch to, in one case, two inches thick.
Granted, polishing the fuel may be a
good first step, if you are close to help, but if the bottoms retain the stuff
that will clog up the filters, being offshore is a bad place to discover it.
This is one area where assumptions can come back to haunt you unless you take
the time to find out for sure.
Rudy
Having run and maintained single screw
trawlers for decades, I agree with Rudy on the polishing issue. Waste of time
and money in most cases. Better to spend your money on tandem fuel filters
that you can switch over to on the fly. As well as installing water alarms
with sensors in the filter bodies. Money better spent than vacuum gauges for
low HP diesels IMHO.
And go up a filter size. Say 900 Racors instead of
500s. Way more filter surface area. So it takes a lot more crap to clog them.
As to crossing in a NW or NE wind, I've found 5 - 10 kt is no big deal. And
a real NE or NW wind 10 - 15 kt is do-able as long as it hasn't been blowing
steady for days. Anything due N is, of course, more problematic.
Capt. Bill
We have tandem Racor 500s on our single FL-135 with 2 micron filters and
used them underway to polish fuel during our 5500 mile cruise to the Bay
of Fundy and back this summer. The PO had used the boat to travel
between Florida and the Bahamas (where they'd sit at a yacht club) for
a number of years and that didn't come close to keeping the fuel
"fresh." When we first started the trip, I was switching the handle
about every 50 hours of operating time; by the time we finished the trip
we were getting more than 150 hours underway before having to switch.
Not a big deal - when the engine started to lose rpms, it took all no
more than 60 seconds to open the engine room hatch, check the vacuum
gauge, reach down and turn the handle to the fresh filter; that evening
I'd change out the clogged filter.
The cost of a polishing system, or paying some commercial outfit to
clean the fuel, would sure pay for a heck of a lot of filters. Of
course, the tandem Racor setup ain't cheap, and ours came with the boat!
If it didn't, I'd seriously consider installing the tandem setup with a
single engine. Our system also has another Racor 500 with a 10 micron
filter between the tandem 500s (with 2 micron filters) and the fuel
tanks, so it filters out some of the big stuff before it even gets to
the 2 micron filters.
I'd also add that going from a 500 to a 900 Racor isn't necessarily a
viable option. Some engines (Ford-Lehmans, for one) don't pull enough
fuel to properly operate a Racor 900 fitler system.
<><><><><><><><><><><><>Mozilla Thunderbird<><><><><><><><><><>
Bob McLeran and Judy Young Manatee Cove Marina
MV Sanderling Patrick Air Force Base
DeFever 41 Trawler Melbourne, Florida
On 1/8/2009 6:31 PM, A H FOSTER wrote:
Having run and maintained single screw trawlers for decades, I agree with Rudy on the polishing issue. Waste of time and money in most cases. Better to spend your money on tandem fuel filters that you can switch over to on the fly. As well as installing water alarms with sensors in the filter bodies. Money better spent than vacuum gauges for low HP diesels IMHO.
And go up a filter size. Say 900 Racors instead of 500s. Way more filter surface area. So it takes a lot more crap to clog them.
I'd have to differ with that. My Krogen has Racor 900's for both the Lehman
135 main engine and the 8KW Westerbeke genset. Both work fine and have for
the life of the boat. If you're thinking about the "turbine" action
separating water, I believe that's been proven to be an urban legend in any
engines used on our size boats.
Keith
Health is merely the slowest possible rate at which one can die.
----- Original Message -----
From: "Bob McLeran" rmcleran@ix.netcom.com
I'd also add that going from a 500 to a 900 Racor isn't necessarily a
viable option. Some engines (Ford-Lehmans, for one) don't pull enough
fuel to properly operate a Racor 900 fitler system.
Big fuel tanks accumulate dirt and are not easy to clean. Here's one
solution:
Our (1961) boat was built with a 120-liter "service tank" in the
engine room. All diesel consumers draw from this tank. The line
coming from the main (3,300 liter) tank in the bow pumps through a
series of filters before entering the service tank. All fuel from the
service tank then goes into a Racor 500, then into a manifold, then
each engine has its own filter series.
As had been pointed out, if you polish the fuel and return it to the
main tank, you're cleaning the fuel, not the tank. But if you store
polished fuel in a service tank (which is smaller and easier to
clean), you have better chances of keeping dirt out of your engine.
The drawback is, of course, that you have to constantly monitor the
fuel in the service tank to make sure you don't run dry. In our case,
the service tank contains enough fuel to run 10-11 hours (which
covers most of our trips), but we refill it at the halfway mark
nevertheless. A bonus is that the graduated sight gauge on the
service tank makes it easy for us to monitor our fuel consumption by
the hour. We clean the service tank once or twice a year, and haven't
ever found much dirt.
One important point made by an engineer who surveyed our boat is that
the service tank must NOT be located so high as to put too much of a
pressure head on the fuel injection pumps. This can lead to leaking
at weak points of the fuel circuit while the engine is shut down
(it's a 48-year-old engine), which could be inconvenient or even
disastrous.
Rafael