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Hydraulic Drive Units 2017-07-04T11:59:16+00:00

HYDRAULIC DRIVE UNITS

Some narrowboats use hydraulics to turn the propeller. Engines can be sited away from under the helm and vibration is dramatically reduced by eliminating gearbox and prop-shaft drive units on narrow boats.

Hydraulic drive system on a narrowboat
A widebeam eurocruiser can often be seen with a hydraulic drive system
Hydraulic drive systems can provide a social space for passengers on a narrowboat stern

Hydraulic Drive Units… An Overview

The whole prop shaft, flexible coupling and conventional gearbox arrangement on a a narrowboat can be replaced with a hydraulically driven pod.

How It Works

An engine driven hydraulic pump is bolted where a conventional gearbox would be on a narrow boat. Hydraulic hose runs to a specially constructed pod, mounted where the conventional stern gland located. The pod has a through hull sealed tube which connects on the outside to the propeller.

There are other components to the overall system such as an oil reservoir, oil cooler and oil flow controller which allows the propeller to be spun through forward, reverse and neutral, but that’s essentially how it works.

Advantages are that the engine does not have to be in the stern. Hydraulic hoses replace the run of a prop shaft, freeing space and making for a quieter steering position. Vibration from conventional revolving components is reduced and the engine does not have to be aligned with propulsion components.

It’s not all win. These systems are not only more expensive than a conventional drive, they are also less efficient. It is a fact of fluid engineering that efficiencies are determined by flow and friction losses plus leakage & compressibility. Thus the further away from the propeller the pump is, the harder it has to work. Additionally, wear over time in service will increase internal leakage. Both these factors are infinitely variable on a narrow boat installation and will only get worse over time.

The decision, as we see repeatedly comes down to what you as an individual really needs and your budget. Seeking advice from the professionals is always the way to go when considering anything out of the ordinary but hopefully we have given you some food for thought.

Hydraulic Drive Units

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