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engine size

would a perkins 4108 or bmc 1.8 be big enough to power a 50ftx10ft widebeam narrowboat style with standard steel spec.also what prop size would i need thanks

Asked by: christopher smith  | 1.26pm, Sunday 2 January

WW says:

Hello Christopher
Either engine would provide plenty of power for nornal use on both river and canal work. I can speak from experience of several BMC 1.8 engines in my own boats, they are a little noisier than the more modern engines but this is easily outweighed by being easy to work on and understand, they also sip the fuel rather gently, four hours per gallon being normal for a narrow beam. Base engines and spare parts are easy and cheap to obtain. If you are considering converting or "marinising" your own engine there are plenty of suppliers of the necessary parts,gearboxes,etc. Calcutt Boats being one of the most experienced. The size of prop depends on the type and reduction ratio of the gearbox chosen and the size of hull appature for the prop to swing. The best advice on this will come from the supplier of the engine or marinising components/gearbox. Following this advice always gave me a 17" Dia X 12"Pitch with a 2 to 1 reduction gearbox, it always worked well for me!
Best of luck with the project.

Mike Jordan  | 6.32PM, Sunday 2 January

I agree with Mike, a BL1.8 would probably be the best choice, though the power on tidal rivers might mean that the engine would have to work quite hard.It would be worth allowing it to power at the higher rating, than the lower, 30hp rating given as standard.
Calcutt still produce the 1.8 BMC from new (though stocks are running low and might now be only reconditioned), and offer a wide range of reconditioned engines, in different states, along with accessories and upgrades and will also recondition your own engine.
BL1.8's can be prone to oil leakage (rocker box and piston rings) and sometimes fracture forward legs, otherwise, are generally reliable. Better coupled to a oil-operated gearbox (I have a PRM Delta on mine) than a mechanical operated one.
Care is needed with cooling tanks, assuming keel (skin tank) cooling, as, if it has to work rather hard on rivers, then you will need good sized tanks- many boats use undersized tanks.
The Perkins 4.108 has a good pedigree, particularly in river boats (such as wide-beam cruisers), however, I have found that it tends to sludge up more at lower speeds, and tends to work best with a freshwater cooling system and wet exhaust, than keel cooling, as it can be prone to overheating a tad more! Then again, I know that some owners would be very happy with their 4.108 and 4.107 (its predecessor!). the starting can also be a bit erratic than the BMC, relying heavily on starter plugs- though older BMC's can be a pain to start if they oil up or lose compression as well!
Best of luck- any further questions, give us a shout!

Mark Langley  | 10.20PM, Sunday 2 January

Readers say:

thanks for the quick response.i think i will go for the bmc

christopher smith  | 7.39PM, Sunday 2 January

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