If you live near near a lake,
river or canal, boating
is a very
in the UK, there are some 40,000 boats. Many are canal boats or
But there are many open day boats. rowing
boats, skiffs, dorys, even canoes.
of the inland boats are over engined. Yes, a coastal boat does
tens of horsepower to be able to counter tide, wind and
Inland there are no such challenges.
boat needs something of the order of 50 watts to propel it for
There are 746 watts to a horsepower.
tenth of a horse power – 74.6 watts - is enough to push a
small rowing boat.
Frequently, a 12 ft cabinless, or
open day boat, has a 5 hp outboard motor slung at the back.
boats have a maximum hull speed. As the power at the back of the
boat is increased,
so does the wave at the front of the boat - the
bow wave gets bigger. All the extra power does,
is to tilt the boat up at the front. It is climbing its own bow wave.
is a “hard” limit. It is called the maximum hull
speed. For a 12ft boat it is 4.6 mph.
But then, just as
our roads have speed limits, so do our waterways. In the UK, it is
So 10 hp, 20 hp, even 40 hp outboards for small
inland waterway boats, are just ludicrous.
40 hp is
needed for waterskiing, but, inland, that is only sensible in
special water skiing lakes.
Tidal waters need low tens of
horsepower. A slim hull in still waters? How about 2 hp or less?
there is the noise. At tickover, the average outboard is
As soon as the engine is revved up – put
under load – the noise soars.
I have measured a 2.3
horsepower (new) at 90+ decibels. You can’t even shout
against that. This is the level where hearing damage starts. And
this is for a leisure boat?
So, let’s go
electric. They’re silent you know – and none of those
poisonous exhaust fumes.
Let’s cut CO2 emissions!
Lady Astor’s 1920’s
electric canoe has been recently restored at Cliveden in the
They were (and still are?) all the fashion.
snag about lead acid batteries powering electrical devices is that they decline.
year you are doing 5 mph – say for 6 hours – then the
batteries need recharging.
Next year, the control unit will
keep you going at 5 mph – but for less than 6 hours.
year you loose range, then you loose top speed.
can’t replace a single battery – they all need
replacing. Say six batteries, certainly at £100 each. My
friend has some “hi spec” batteries – just four
of them - £400 each.
And that’s cheaper
than Lithium ion batteries. They are 5+ times more
She is advised by the installer to cruise at
10 amps. It’s a 24 volt system.
Watts = Volts x
When cruising, she is powered by 24 x 10 = 240 watts =
0.32 of a horsepower.
converted to electric because her old 1.5 hp petrol Stuart Turner
was too noisy
and was a real “pig” vs reliability.
The boat is now quiet and reliable, but is just far, far slower. Not enough horsepower.
Stirling provide a better solution?
A Stirling engine is very quiet –
I have measured 40 decibels when cruising.
The engine runs
at the same noise level as the breeze and the birds.
is reliable. My Stirling boat engine was built 21 years ago.
have had one mechanical failure. There was a poor weld in one of
It only does 3.2 mph. I would like more
– but that raises the crucial point.
DO YOU BUY A STIRLING BOAT ENGINE!!!