Building Harnser
harnser 2



Harnser is a 57ft Tug style steel narrowboat with a gross weight of approximately 18 tonnes. The hull was built by Marque Narrowboats of Eccelshall, Staffs. and carries the unique hull number of 063.

The Steel used is 10, 6, 5 and 4 mm to BS4360 Grade 43A. All glass is toughened to BS standard 857/2 or 6206 and the only hull penetrations below 10” above the waterline are for grey water discharge and are plumbed to above the 10” level inside the boat.

The fore and stern decks have internal drainage which exit the hull above the 10” level. Under the stern deck there is a weed hatch to give access to the propeller. This has an up stand of 10“ and a sealed, clamp down lid.

There are 3 points on the Port side gunwale for bunkering and pumping out. At the stern is the diesel bunkering filler, half way along the gunwale is the black water pump out point and at the fore end of the cabin is the potable water filling point. All three are brass construction and are labelled as to their use.

Access and Egress is via double doors at the bow and the stern of the vessel. In addition to this there are 2 side hatches on each side of the vessel that can be used as emergency exits.

Power Unit

It is main propulsion powered by a Beta Marine BD3 3 cylinder diesel tug engine with the final drive via a Voac hydraulic system.


BD3 diesel engine with mechanical engine stop, cable operated from the steering. The engine is fitted with a fuel filter and an Agglomerator on the engine, both with metal filter bowls. There is a further filter mounted on the Starboard swim adjacent to the main diesel tank, this also has a metal bowl. All fuel piping is metal with the exception of a short flexible run in the supply and return lines, between the engine skid and the bulkhead. Both these lines are manufactured in accordance with ISO 7840

The engine is water cooled with a closed loop system pumping water through a skin transfer tank on the port swim. Hot water is also pumped through the lower coil of the calorifier

The engine is mounted on hard wood beams bolted to steel bearers which are welded to the base plate of the hull, this also acts as a drip tray for the engine preventing any spillage entering the bilge.

The engine works of a speed band of 400 to 1200 RPM and is controlled by a “speed wheel” at the steering position.

The engine is fitted with two alternators, a 12 volt unit to charge engine batteries and a 24 volt unit to charge domestic batteries.

Hydraulic Drive System

The engine drives a hydraulic positive displacement pump which draws oil from a storage tank mounted above the engine and in turn delivers it under high pressure to the “control valve block”, from here oil is directed to the main “hydraulic motor” and the hydraulic “bowthruster”. Spent oil is then returned to the oil storage tank via a heat exchanger where it is cooled with water returning from the skin tank to the engine cooling system.

Hydraulic oil storage tank

Hydraulic oil is stored in a steel tank mounted above the engine. The tank is fitted with a sight glass/thermometer, it also has a filter to filter the return spent oil before its used again. The tank has a capacity of 32 lt. And normally runs with approximately 28 Lt of oil

Hydraulic Pump

This is Voac unit with a capacity of 40 cc. I.e. It pumps 40 cc of oil per revolution of the pump shaft. It’s output volume is directly proportional to the speed of the engine and is capable of very high pressure. The input shaft of the pump is coupled to the crank shaft of the engine by an R&D coupling, this is a direct drive with no clutch/gearbox.

Control Valve block

The control valve consists of two control valves mated together, flow and pressure relief valves. The first valve is operated mechanically by a cable from the gear change knob. This has three positions, central, neutral which re-circulate the oil back to the storage tank. Down, forward which directs pressurized oil to the main motor to rotate it in an anticlockwise direction and directs the spent oil back to the storage tank. Up, reverse which directs the oil to rotate the motor clockwise and the spent oil back to the tank.

The second valve is electrically operated for the bowthruster. This valve is operated electrically by a rocker switch to give Port or Starboard thrust as required from the steering position. As with the main valve, oil is routed to the hydraulic motor on the bowthruster to give the required direction of thrust, As the bowthruster has a lower pressure and flow rating that the possible output of the pump, the circuit includes flow control and pressure relief valves.

Main Motor

The main hydraulic motor is a bi-directional Voac motor, with a capacity of 80 cc i.e. It requires an input of 80 cc for one rotation of the output shaft This is equivalent of two rotations of the engine to give the 2 to 1 final drive ratio.

The main motor is mounted on 3 flexible mounts and the motor shaft is connected to propeller shaft by a Fenerflex coupling.


The bowthruster s a Crann hydraulic unit and is mounted in the bowthruster tube in the bow of the vessel.

Pipe work

All pipes both flow and return are of reinforced flexible construction with crimped screw connections on each end. All hoses are rated for the maximum presser available.

Diesel System

There are two diesel tanks. the main tank is approximately 300 lt. and is built in to the stern of the boat. This feeds diesel to both the engine and the Day Tank. Take off points are at high level on the starboard side of the boat and each is fitted with an isolation valve.

The other tank is a day tank specifically to feed the diesel fired cooker. This is mounted in the engine room and has a capacity of 23 lt. This tank is fitted with an overflow to return excessive diesel back to the main fuel tank. There are two takeoff points for this tank, both are at the bottom of the tank and are fitted with isolation valves, one feeds the diesel cooker, the other is a drain fitted with a plug.

Diesel is transferred from the main tank to the day tank by two methods. The primary method is the engine spill rail including the self bleeding vents are piped to the top of the tank, This means that whenever the engine is running the day tank is being toped up until it overflows back to the main tank. In addition to this there is a small electric fuel pump. This pump is controlled by a timer relay that is energized when the main engine is starter is energized. This is normally left electrically isolated

Both Tanks have there own vents installed to comply the BSS (Boat Safety Scheme) and are filled via a single filler point on the port side of the rear deck, this is constructed to prevent diesel spillage entering the boat.


Ventilation is both at low level and through the roof.

Low level is via a louvered grill the stern bulkhead on the starboard side that opens into the wet clothing hanging area. At the bow a louvered grill is fitted into the tunnel light mast, from here ventilation is ducted to the floor level below the fitted sofa.

High level ventilation is via 3 roof mounted ventilation mushrooms , built-in ventilation area below the glazed units in pigeon box above the galley of 276 cm sq. and 45 cm sq around the engine room pigeon box

Electrical System

Harnser has 3 voltages available:

12 volts DC for engine ancillaries and items that are on required when the engine is running, i.e. Tunnel light, horn, etc. This is supplied from one 12 volt batteries. This also provide supply to power the bilge pump. This battery is charged by the main engine 12 volt alternator.

24 Volts DC for domestic use, i.e. Lighting, Water pumps and supply to the inverter. This is provided by 4 X 110 ah 6 Volt batteries connected in a series to give a 24 Volts output. These batteries are charged by a secondary 24 Volt alternator mounted on the engine controlled by an Adverc battery management system. The state of charge is monitored by a Sterling battery management panel.

240 Volts AC for domestic equipment, i.e. TV, DVD player and Refrigerator. This is supplied by a 1500 Watt 24 Volt DC to 240 Volt AC Inverter. All circuits are routed via a RCB and MCBs There is also a socket to accept a shore supply.

All supplies with the exception of the bilge pump are isolated by 2 main battery isolator switches mounted in the engine room adjacent to the end of the battery banks. All circuits have individual overload circuit breakers.

The negative line of all the batteries and the 240 AC earth are all bonded to the boat hull in the engine room on the Port engine bearer


The galley is equipped with a Dickinson Adriatic diesel cooker that also heats the water and serves as a space heater for the forward part of the boat. Water heating is by a half turn stainless steel heating coil in the top of the cooker burner pot. This feed directly to the calorifier at high level. The return water is taken from the calorifier at low level and returns to the heating coil via a heated towel rail in the bathroom. Excess heat from the water is dispersed through a radiator mounted at the forward end of the lounge. This is fed via a 24 volt Johnson electric pump controlled by a thermostat sensing the temperature of the calorifier.
The diesel supply for this comes from a dedicated tank (Day Tank) mounted in the engine room. There is an isolation valve on the tank discharge and a second valve in the bathroom (This was the closest it was practical to fit a valve to the appliance as the diesel supply comes through the bulkhead behind the cooked to feed it) There is a “FireSafe Valve” connected in the cooker supply line. This valve is mounted in the vanity unit in the bathroom with the capillary sensor mounted in the cooker above the control valve, so in the event of the cooker control valve failing and the unit overheating the supply oil would be automatically isolated.

Potable Water

The Potable Water Tank is housed under the bed under the fore deck, it has a capacity of approximately 450 lt. The contents of the tank are monitored with a MSC Tank monitor. It is filled from a deck filler on the Port gunwale. The water is pressurized to approximately 3 Bar by an electric pump with integral pressure switch under the galley cupboard floor and pressure fluctuations are controlled with an accumulator.

There is a 12 Gallon hot water calorifier in the bathroom, this is fitted with twin heating coils to heat the water from both the engine and the cooker.

The cold water is fed to the bottom of the calorifier via a non-return to prevent hot water feeding back to the cold water system. Hot water is draw off from the top of the cylinder and distributed to the hot water taps and shower. To allow for the pressure increase due to hot water expansion the hot water circuit is also fitted with an expansion accumulator. For safety the calorifier cylinder is fitted with a presser relief valve that discharges into the bathroom vanity unit sink waste.

Waste discharge

Grey water from the galley sink and the bathroom vanity unit discharge by gravity through the hull sides overboard. The bath being below the waterline is emptied by pump into the vanity unit discharge pipe. This pump can also be used to empty the hot water calorifier.
There is no black water discharge overboard. The toilet discharges into a holding tank which is emptied by vacuum at designated sanitary disposal points.

Safety Equipment

Harnser is fitted with three 1Kg ABC Powder fire extinguishes to BS EN3 each with a fire fighting capacity of 8A 55B. These are mounted in the lounge on the starboard side, in the engine room on the starboard side against the head lining, in the boatman’s cabin by the rear doors and a Fire Blanket in the galley. A Life ring is can be carried on the roof whilst cruising rivers. There are two self inflating Lifejackets carried in the storage area under the forward bed. An anchor is also carried whilst cruising rivers.

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