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How much Horse Power does a Narrowboat Need?

I am new to boating, but loved my first narrowboat holiday last year, and am considering whether to buy my own boat. Living in Derby, I would probably want to navigate the river Trent at some point. How much horse power should a narrowboat in the 40 - 60 foot range require for river cruising?

Asked by: Rod Nelson  | 12.28pm, Tuesday 10 March


WW says:

The size of engine for a narrowboat is very dependent on the use; as just pottering around the canals does need very much power, however for river use more power is a good idea.
Too large an engine gives poor fuel consumption for canal cruising and continual running at low power levels is not good for the engine. It is much better to work a smaller engine hard; to this end it is important to specify a large skin tank cooling surface so that the engine can run at full power for long periods such as will be needed for river work.
Underwater profile has a large effect on the power requirement, many canal boats are built to give maximum cabin space to the detriment of smooth water flow. Short bow profiles and poor swim design give boats that need more power to push them through the water.
The working boats of old have good hull shapes and relatively small engines 15-20HP.

Rupert Smedley  | 1.26PM, Tuesday 10 March

A better way to look at engines is more the torque they produce- and this is closely related to engine cubic capacity, certainly for typical medium-light industrial bases engines typically used in Narrowboats in the last forty years.
As a guide, around 1.3 to 1.5 litres for boats between 30 and 40ft, 1.5 to 1.8 litres for boats up to 60 and up to 2 litre for boats up to full length.
Some high powered engines (in hp terms) for seagoing craft are quite small capacity, while as Rupert points out, traditional engines in older boats are quite low hp but have high torque and cubic capacity.
Some big modern diesels are too large for many Narrowboats- and over time, slow speed running with lead to problems such as carbonisation. Better to have a alightly smaller engine working harder than one too big which hardly goes much beyond tickover.

Mark Langley  | 11.11PM, Tuesday 10 March

As for skin tanks, to work effectively on rivers, you need a skin tank (fitted with an internal baffle for preference) that should be at least 1 sq ft of surface area per 4hp of engine power. Larger tanks are even better- and the tank should be as thin as possible to minimise coolant volume

Mark Langley  | 11.13PM, Tuesday 10 March

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