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Engine size

I'm interested in buying a 60ft narrow boat that has a barrus shire 40 Hp with a 17x12 prop ,I plan to cruise the river Trent and soar as well as the canals , is 40 hp on a 60 ft boat adequate
Wayne

Asked by: wayne rook  | 8.31pm, Wednesday 29 March


WW says:

Yes, too big an engine will be under used on canal cruising. Do ensure that the cooling system will cope with the engine being run at high levels if you wish to do river cruising, many narrowboats have poorly designed skin cooling that will not dissapate the heat.

Rupert Smedley  | 11.20PM, Wednesday 29 March

I have a 42hp engine on my 60ft boat (previously 35hp) and both are absolutely fine for tidal and non-tidal waterways.
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A Rupert says, having a large enough cooling tank is important (and also well-deseigned). They should be at least 1sq ft for every 4 hp (so a 40hp engine should have at least 10sq ft in total area) and they should be as thin as possible. Ideally, they should have a single internal baffle, so that water flows in a C shape to maximise contact time with the water outside. Usuall, an indication of this is that the feed and return pipes are at the same end of the skin tank- if they are at opposite ends, it usually suggests a lack of internal baffle.

Mark Langley  | 9.46AM, Monday 3 April

I should also add, when an engine is working hard, good ventilation to the engine space is important to help dissipate heat as well (around 10% of engine thermal load is transferred to the air surrounding the engine) so good ventilation is important. Barrus would suggest 1sq inch of ventilation per hp (40 in total for a 40hp engine) into two vents- ideally one higher (to let hot air out) and one lower (to let cold air in). However, more boats make do with one or two smaller vents- improvements are easy made. Better ventilation can also help with alternator life as well, as running hot doesn't help them.

Mark Langley  | 9.49AM, Monday 3 April


Readers say:

Thank you appreciate your advice , I'm thinking of changing pump out for a thetford cassette , does anyone have any idea on how much this would cost approx cheers wayne

wayne rook  | 6.09PM, Monday 3 April

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