Mechanical
Mounting a Depth Sounder under a
Houseboat
Water Pumps and Accumulator Tanks
Does your water pump continually cycle off and on when
you open a tap slightly, or when you are running an
evaporative air-conditioner? Or do you get water hammer when
you turn your taps off and on? Do you have trouble
controlling the temperature of the hot water because of
water flow variations? If so, then you may need to consider
adding an accumulator tank to your water system.
What is an Accumulator Tank?
An
accumulator tank is
a pressurised container that attaches to the output line of
your pump. It is pressurised to the normal output pressure
of the pump and provides a small reservoir that supplies
water when a tap is turned on. When the reservoir starts to
empty, the pump comes on and refills the reservoir and then
stops. This means that the pump runs less often and comes on
fully when it does.
This results in a smoother water flow, reduces water
hammer and decreases on/off cycling of the pump increasing
its lifetime and reducing battery consumption and operating
noise. The smoother water flow also gives better control of
the temperature of hot water. If you have a houseboat with
evaporative air conditioning, you will find an accumulator
pump will prevent the water pump cycling so often, allowing
it to run much cooler and last longer.
Experiences
with a four-stroke outboard
by
Michael
Heuzenroeder and
Sue Holland
With the
inevitable
banning by attrition of two-stroke outboard motors on the Murray, we
felt some of our members who might be considering re-powering their
vessels might be interested with our experiences with a four-stroke
outboard motor.
In August
2001 we
purchased a Mercury 25hp "Bigfoot" four-stroke outboard (Sue's birthday
present) to replace a tired and very thirsty Johnson 70hp on "Feral
Boat Fred" which is a 23' alloy cruiser weighing in at more than 2
tonnes when fully laden. Being a four-stroke the economy from the
Mercury is outstanding at 3000rpm (about 5 mph/8 kph) where it uses
about 3
lph or less, however, we usually cruise at 3,500rpm (6 mph/10 kph) and
still
get around 3.5 lph. Recently we covered about 600km on the Murray that
included the 2004 Ramble and used approximately 200l of fuel. At low
revolutions the engine is very quiet, this initial advantage over the
two-stroke diminishes as engine revolutions rise. Ease of starting is
outstanding with one turn of the key it always starts like a new car,
with smooth idling, no blue smoke or smell of incompletely burnt fuel.
Prolonged low speed operation does not result in fouled spark plugs and
rough running that can often be the case with two-stroke motors.
The
"Bigfoot" high
thrust leg is perfect for displacement hull boats, where high speed is
not an issue. This technology enables lower power engines to turn much
larger diameter propellers (12.5" diameter x 8" pitch in our case)
generating greater thrust. This is achieved by the use of lower gearing
of 2.42:1 in comparison to around 2:1 in a "normal" outboard leg to
drive the prop. Mercury uses a modified 50hp leg on the 25hp Bigfoot.
This extra thrust is particularly useful when dealing with high winds.
Both the
Mercury Bigfoot
and Yamaha 25hp high thrust motors share the same power-heads, but have
different legs and propellers that are made by the respective
companies. Many parts for the power-head are interchangeable between
the two brands. The motor is simple with only 2 cylinders of 500cc
capacity with a single carburettor and belt driven overhead camshaft
operating two valves per cylinder. Ignition and timing is
electronically controlled and should be trouble free, the alternator
output is 15A which is plenty of charging power for an outboard.
Overall the motor has a wonderful twin cylinder "throb" when underway
and gives a "working boat" reliable feeling. We have done over 400
hours with our motor and have had no problems of any type.
What are
the
disadvantages? The initial cost in comparison with a comparable
two-stroke of similar horsepower is high (we lived on baked beans for a
year!) and the weight of the motor (about 90kg) makes power tilt and
trim pretty well mandatory. Service costs are also higher, requiring
oil change and oil filter at every hundred hours, the rest of the
service is much the same as for a two-stroke motor. Because of the
inherent simplicity of the Mercury/Yamaha design basic servicing is
certainly not beyond mechanically minded owners.
There
have been many
recent advances in two-stoke technology that have resulted in huge
increases in their fuel efficiency and environmental friendliness which
should cause a rethink about the merits of the latest technology
two-stroke outboard motors by government. Until this happens, despite
their weight and initial purchase price the four-stroke outboard motor
offers many advantages when travelling the Murray or when thinking
about re-powering your vessel.
If
you have "Tips and Tricks" of your own please e-mail (in any digital
format) the Webmaster
with your contribution.
©RMBOA
2005-2007
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