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Bow thrusters

What is the performance difference between hydraulic and electric bow thrusters? When does the kgf rating become overpowered(cavitation in 3' of water?)for a 70'nb?

Asked by: connol coan  | 4.17pm, Saturday 12 September

WW says:

Hydraulic bow thrusters usually use a pump, which runs off the engine (much like a second alternator), which pressurises hydraulic fluid in a supply line (usually flexible or steel pipework) leading to another hydraulic pump on the bowthruster which does the work.
An electric bow thruster has a fairly heavy-duty electric motor powering the thruster directly (and needing a large current to do so).
Hydraulic bow thrusters work very well in continual use situations, although the ultimate power is much more closely linked to engine RPM- and usually as most mmaneouvres are done around tickover, this has to be designed in.
Electric thrusters are much cheaper, but often have a tendancy to overheat/cut out ro drain their dedicated batteries.
For the size of bow thruster likely to be fitted to a 70' narrowboat, cavitation is not likely to be a problem; however, ventilation (where air is drawn into the tube) is more likely. The tube diameters specified by the manufacturer will deal effectively with cavitation, but a poor tube design can suck in air.
Do you really need a bowthruster? They are often overused and, although they can be convienient, could you still handle the boat if it fails? They are not always the most reliable bits of equipment aboard boats!

Mark Langley  | 10.03PM, Tuesday 15 September

Readers say:

I agree that Bow Thrusters are more of a feel safer factor than a necessary piece of equipment.I am hoping to get one which in the process of development whereby it will have a variable speed so that if I am single handed I will be able to keep the bow gentle thrusting against the bank while I tie up the stern.

connol coan  | 10.17PM, Wednesday 30 September

A good friend and myself are thinking about buying a narrowboat jointly, probably 50-60ft. I will quite often be boating single handed and would like fellow boaters opinion of the necessity for a bow thruster? How much do they cost to fit? Many thanks.

Martin jenkins  | 9.35PM, Thursday 31 August

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