Speed vs RPM, Fuel tank cleaning


John and Anne on Bali Hai <hollamby@...>
 

In previous years I have found my Autoprop severely fouled after
leaving the boat in the water in the winter. This resulted in very
low engine revs until cleared. During the last haul out May 05 I
polished the prop and used Pellerclean. Several times during the
season I found that the engine revs were limited and dived to find
that the prop was fouled but only with lime/coral type encrustation
to a depth of about one eigth of an inch (2-3mm). It was quite hard
to remove and I am not impressed with Pellerclean. The boat spent
all last season in Malta in a marina which is relatively clean as
there are very few live/crap aboard owners. My test for build up is
to motor at full throttle to check that I can get 3,300 rpm. The
lime scale reduced this to about 2,200!I then cut the revs back to
take the unfair load off the engine until I clean the prop.
I have a hose about 10 metres long which I connect to the regulator
on the air bottle and to a spare mouthpiece so that I can deal with
the underside using only fins, wet suit,weight belt and gloves.
So far as carbon build up on the turbo is concerned I follow Yanmars
insructions and before turning off I rev up out of gear to 3,000+
for a few seconds and repeat if necessary to burn off any carbon
which comes out of the exhaust as white smoke. It is then important
to let the engine idle for a few minutes to allow it to cool and
lubricate the turbo.

My last boat had three tubes into the fuel tank, two for fuel out
and return and one for a heater.The fuel out and heater tubes went
into a filter which consisted of two brass plates separated by a
strip of mesh around the edge to act as the filter. A build up of
algae on the filter completely blocked it and it compressed like an
accordian! Luckily the tank was nearly empty so I was able to get at
the filter to remove it and throw it away. I then arranged the fuel
out pipe so that it was a couple of inches above the bottom of the
tank and put the unused heater pipe right down to the bottom of the
tank. This meant that I could connect a plastic tube to the top from
time to time to a small electric pump which was connected to another
tube to discharge the water and other grot into old clear plasic
bottles so that I could see when all the crud had been removed. I
then let the crud settle at the bottom of the bottles and decanted
the clean fuel back into the tank.
I have cleaned out the bottom of my Amel tank a couple of years ago
when it was nearly empty. I did this by removing the inspection
plate and putting a pipe down to the bottom and then pumping out
some of the contents into some big plastic tanks and then scrubbing
the bottom etc of the tank with a paint brush lashed onto end of the
pipe. Note the lashing must be tight and tape must not be used.
The dirty fuel was allowed to settle and most was poured back into
the tank through a Baha filter using only the finest mesh as this
leaves lots of room to avoid over flows, I never use the coarse and
medium mesh filters.I suspect that a prime cause of blockages is
adding algae killer to infected fuel. I now put my long copper tube
down to the very bottom of the tank every year and suck out any
crud/water which has settled whilst the boat is not in use.
One day,when the tank is nearly empty I will drain it and throw away
the internal filter.

Best wishes to all, John, SM 319

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