Propulsion and fuel options.

In this section we will cover the ‘vision’ for the boat, and how this can be achieved while at the same time providing notes that might be useful for other craft.  I believe the information to be correct, but details may change as new information comes to light, experience is gained and products change.

The Vision.

When I first started thinking about building a narrow boat, I reflected on my previous experience of hiring and being around them.  I enjoyed the independence, not ‘being on the grid’ self-sufficiency.  I soon learned this is only an illusion as eventually the fuel would run out.  What I was less keen on was the noise of the engines especially the noisy modern hire boats.  I also discovered this was not the only solution, there are charming sounding old Lister engines puttering, some very well insulated modern engines are quieter, and the steam version chugging along are fascinating.

What I eventually decided I wanted, if possible, was a boat that did not need to use gas or oil and was quiet.  I’m not aiming for an environmental award, I’m trying to avoid big fuel bills, and achieve silent operation.  With no oil or gas, the boat safety certificate should be easier too.  As much as possible I want to be self-sufficient.  To realise such a vision there are a host of issues to consider such as the nature of the propulsion, access to and storage of fuel, range availability, safety and compliance with the Vision goals.

Power options

The fuel options for inland waterways are petrol, steam, horse, diesel, hybrid, and electric. The use of horses would be wonderful, but I fear not very practical.  For me steam is in a similar situation, it does not have the ‘instant availability’ of the other systems, not to mention the maintenance issues associated with boilers etc.  Petrol is an option but more commonly used on smaller craft or those looking for higher speeds.  Because of the issues associated with the storage of the fuel this is not really an option I want to consider as a principle power source. That leaves Diesel, Hybrid and Electric.

Diesel can be made quieter, but even the best sound insulation can not remove all the sound and vibration.  Range is limited to the size of your tanks and how much fuel you can afford.  Sadly, it only ever seems to get more expensive.  It is a well proven technology, and relatively easy to install and operate with ready availability.

Hybrid systems based on diesel engines seem to give the best of both worlds.  You have power when you want it and you can run on batteries for short periods when you want quiet.  However, they also have all the limitations of diesel too, fuel storage, and usage, along with sound at some point when charging is required.

Electric systems are certainly quiet, but we still need to address the issue of power storage, its availability, and the range.  It is not a proven technology (yet) and therefore brings with it some degree of risk.

How much power is needed?

On most canals in the UK, speed is limited to 4 mph (3.5 knots) and therefore engines do not need to be overly powerful, however there are factors that should be additionally considered to ensure that there is a surplus of power/thrust available if needed.  If the Narrowboat, is to be used in rivers with fast flows or estuaries with strong tides, the power/trust would need to be able to exceed a greater speed than that of the flow or tide to enable headway to be made.  Safety and maneuverability, the combined performance of the engine, gearbox and propeller should be capable of stopping the Narrowboat, within its own length.  The following table is for guidance only and is taken from Beta Marine’s excellent website.

Length 25ft (6 tons) 30ft (7 tons) 35ft (8 tons) 40ft (10 tons) 45ft (12 tons) 60ft (14 tons) 70ft (18 tons) Beta 43 Engine
Power requirement (HP) 13.5 bhp 16 bhp 20 bhp 25 bhp 30 bhp 38 bhp 43 bhp
Diesel Unit Beta 14 Beta 16 Beta 20 Beta 25 Beta 30 Beta 38 Beta 43

If the size of your boat falls between two values, use the next highest value.

Given that my decision is to design and build a 59ft boat a diesel engine of at least 38bhp is required.

When building a hybrid craft the same size motor in terms of horse power will be required.  For an entirely electric drive the following motors as offered by Lynch would be suitable.  There website can be found here.  Lynch offer several motors in addition to these, and certainly for the smaller craft the engines are over specified.  However as with diesel engines it is better to have a little more and not need it that too little and an emergency.  As for the diesel engine a similar 38bhp unit is needed, in this case at least a LEM200 D95B, or perhaps the next size up for that added confidence a LEM200 D135RAG. 

Electric Unit LEM200 127 LEM200 127 LEM200 127 LEM2x2 D126 LEM200 D95B LEM200 D95B LEM200 D135RAG
Electric HP 22 bhp 22 bhp 22 bhp 30 bhp 38 bhp 38 bhp 46 bhp


Fuel Storage and Availability

With a diesel system and for that matter a hybrid, a large tank is required for fuel storage, there are several locations for this, hull sides, under beds, floors etc.  Your imagination is the limit, but all of them need to consider the safety of storing the fuel, and all come with the issue of handling filling of the tanks along with the mess that the task entails.  Your boat builder is probably much better placed than me to go through all these scenarios.  Storing fuel for a fully electric craft needs batteries in place of diesel.  You’ll also need to consider these for a hybrid craft too.  If we keep it simple and only consider a regular car battery type system the storage space will require ventilation, mainly for the gases given off during charging but also to ensure that overheating does not occur.  The space required for a fully electric craft can be quite considerable, we’ll discuss this later in more detail in the section referring to Batteries.

Starting with a diesel craft the availability of fuel is generally marina’s which is fine if you are careful and ensure you do not run out of fuel.  Although I’m sure a walk along a tow path with a fuel tank can be a good way of not forgetting to check your tanks regularly.  Being realistic even with a fully electric boat we can’t get away from the need to visit marina’s, for pump-outs, water etc, so other than cost this is not such a great burden.

Electricity on the other hand can also be acquired from Marina’s, but it can also be generated on board too, e.g using solar panels and wind generators.  Solar panels come in a variety of sizes, although for our purposes units of 150cm x 70cm are ideal for roof mounting while providing minimal obstruction.  To support the use of solar power the addition of wind generators is sensible as the work night and day and especially when there is no light.  How much fuel is needed and how many panels is another matter.

The layout of solar panels is a hotly debated topic, and in an ideal situation they would be perpendicular to the sun for optimal charging which on a moving craft is not realistic.  Even moored it is unlikely a South facing orientation for the side of the boat will always be achieved therefore we are looking for the best compromise.  A popular approach is to have the panels mounted across the boat raised in the middle on which the panel pivots to allow tipping it to one side or the other dependent on the location of the sun.  This can be very effective, but it comes at the cost of increased air-draft for the boat.

Alternatively, and my preferred method is mounting them flush to the surface along the length of the boat.  In this manner at least, half of the panels will always be in more or less the right orientation, with the other half receiving light albeit at a slightly reduced level.  This also has the benefit of minimising the air-draft and avoiding any issues of ropes fouling the solar power frames.

Wind turbines are much easier to fit and need a mount for the pole and to ensure enough height to be clear of people’s heads walking along the side of the boat.  While it is possible to use the windmill style, the diameter of the blades and the tip speeds limit the size of the devices that can be used.  The maximum safe width being 6ft, which would need a mast of at least the same height, which is impractical when dismounting devices for tunnels etc.  Fortunately, we now have a ‘ball’ style horizontal turbine which is circa 1ft in diameter and sits at the top of a pole which only needs to be clear of roof obstructions to operate effectively, circa 1ft should do it for most craft. It also allows easy removal and storage when underway.  In theory any number of these can be used, but for my craft I’m currently thinking of just one for and one aft.

While hiding fuel tanks is an established art, calculating how much space is available on a given craft for solar and wind is not.  To help I’ve out together the following table on the basis of my preferred flush mounting panels, and 2 wind turbines.  I’ve also added allowances for other roof items, wind and light availability etc and calculated the typical daily output.  This will be useful in later calculations. 

Length 20ft (6m) 30ft (9m) 40ft (12m) 50ft (15m) 60ft (18m) 70ft (21 m)



LE 300 marina

Less bow and aft area 5.25m 5.25m 5.25m 5.25m 5.25m 5.25m
Spare roof space 1 1m 1m 1m 1m 1m 1m
Roof vents 0.5m 0.5m 0.5m 0.5m 0.5m 0.5m
Seating area (aft) 1m 1m 1m 1m 1m 1m
Roof storage 2 2m 2m 2m 2m 2m 2m
Solar panel space available 1.5m 4.5m 7.5m 10.5m 13.5m 16.5m
Panel length 1.5m 1.5m 1.5m 1.5m 1.5m 1.5m
Panel width 0.7m 0.7m 0.7m 0.7m 0.7m 0.7m
Panel power (150w) 3 100w 100w 100w 100w 100w 100w
Number of panels available 2x 6x 10x 14x 18x 22x
Estimated daylight hours 4 5hr 5hr 5hr 5hr 5hr 5hr
Solar Panel power/day 1kw 3kw 5kw 7kw 9kw 11kw
 Wind turbine (400w) x2 5 500w 500w 500w 500w 500w 500w
 Estimated wind hours 6 12 12 12 12 12 12
 Wind Turbine power 6kw 6kw 6kw 6kw 6kw 6kw
 Total Daily Power (TDP) 7kw  9kw 11kw 13kw 15kw 17kw
  1.  This is an allowance for fitting around roof furniture such as vents and rope eyes.
  2. It is common to have roof storage sometimes in boxes but other times just a space to rest a bike.
  3. While the panel max power is suggested to be 150w, this is reduced for sub-optimal positioning.
  4. Daylight hours are hours of light, even modestly lit days will generate power.
  5. Assuming two 400w turbines not operating at peak performance (~60%).
  6. This estimates up to 12 hours of breeze per day, gale force winds are not required.

Power Consumption

Having established the power producing potential partciularly of solar and wind we should now look to understand consumption especially important if the boat is not a hybrid or diesel craft.

Always on (24hr/day) Occasional (2hr/day)
Fridge or fridge freezer 250w Washing machine or washer dryer 500w
Computers and control systems 100w Cooker (hobs and oven) 2400w
     Entertainment (TV DVD) 55w
Hot water system (shower, sinks) 2000w

With solar panels (or any other charging system) these can be run from 6, 230 amp/hour leisure batteries (4 for the constant demand, and 2 for the intermittent).  However, as it will destroy or seriously damage a battery to run it completely flat we will double the battery requirement to ensure they do not drop below 50% in any given period, i.e. 12 batteries will be required for 'household' purposes. Note, we have not yet considered power storage for propulsion.


These come in all shapes and sizes.  The most common debate at the moment seems to be wether to use lead acid (car battery type) or lithium.  They require different charging methods so are not easily mixed with out consideration and have a significant price differential, the latter (lithium) being about twice the price.  However, lithium also allow and prefer to be run completely flat, therefore only half the volume are required (see earlier note regarding power consumption).  This is an important point, and the next table looks at the amount of space available on a boat and how it could be used.  If you need more space on board or more range this can easily be obtained by switching to lithium albeit at a higher cost.


Lets start by considering a battery.  Earlier I mentioned lead acid and used a car battery as an example.  In practice, while these could be used they are not the ideal solution as they do not allow deep power useage.  For this we should be looking at 'leisure' batteries which are more tolerant of deep power drain.  Leisure batteries are available in a variety of physical sizes and power ratings, for our purposes we will be using the relatively inexpensive and easy to obtain 12v, 230A/hr AGM version with a physical size of ~10"x11"x21", or 242x273x513 (HxWxL).  Currently these can be purchased for ~£280, (£1.22per A/hr).

The storage of the batteries is relatively easy for an electric boat especially if a traditional design is used with it's 6ft long engine room available.  The simplest layout being to have the batteries on either side of a gangway although it's possible to have a corridor at the side if thats preferred, but do bare in mind the balance of the boat.  With batteries of 513mm length they would be easiest to store end on (long side parrallel to the ends of the boat, and with 1 battery on each side that would allow a corridor in the middle of about 1mtr (1981mm boat width less 2 batteries (513x2=1026) =  955mm (~3ft) less space for any doors to conceal the batteries.


Using this layout each side can store 7 batteries with space for dividers if desired, or 14 for each layer in total.  this would more than cover the household demand.

In terms of battery storage for propulsion, assuming an internal height of ~6ft or 1800mm, at least 6 layers can be stored allowing space for connectors and cabinets.  Deducting 1 layer domestic use, we have 5 layers x 14 batteries at 230A/hr = 16100 A/hr available



Storage volume  half and full ship

Range issues and storage and recharge, how long to recharge?

Deduct domestic and calculate range with peak and cruise for battery volume, half  and full ship

Shore power, inverters etc


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