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quark3364
quark3364

Posted: Wed Aug 07, 2019 2:33pm

Post Subject: Engine size for river cruising

Hi folks anybody advise me on hp for rivers going to be using Severn and Avon yo yo ING between cut cruises will be a live aboard is a 35/38 strong enough. I am a motorcycling hgv mechanic so a little bit of mouse but not enough experience of boat capabilities am in process of sorting a boat out 58/foot ish presently lost in the sweet shop. Cheers

Tony-B
Tony-B

Posted: Wed Aug 07, 2019 3:36pm

Post Subject: Engine size for river cruising

I will assume this is a narrowboat, if not please come back. Traditional boats that can swing a large diameter prop often got by on around 15hp but the skippers could read the water ad knew how to use currents and eddies to their best advantage. Their engine, gearbox and props were well matched and the boats often swam far better than a modern cruising boat. The reason I say this is to illustrate that raw HP is far from the be all and end all of what is required for river cruising. A skipper who knows when its time to tie up and wait fro the flow to abate is also very important. Modern cruising boats tend to have a 20" stern post and that gives a sensible prop side of around 18" diameter. This will need to be driven at a higher speed to get the same push as a larger diameter on would need To try to illustrate it in terms you know about it is a bit like me asking you what motor cycle would eb best to ride the TT course without specifying the tyres to be used, wet or dry roads and telling you about my ability as a rider. Another thing to consider is that the propeller uses torque, not HP. As HP has a speed component you will find that the torque developed in an engine peaks at some point before maximum HP is reached so for optimum economy a typical narrowboat engine will never achieve its quoted HP because the prop load will stop it accelerating beyond the maximum torque point - that is assuming the prop is well matched and far too many are not. I have a 54ft narrowboat with a proper marine engine in it rated at around 35 HP (Bukh DV36) with a propeller specified and supplied by the inland prop specialists and it has coped perfectly well with the Thames in flood and fighting the tide on the Trent so on that basis I would suggest the HPs you mention should be adequate. Definitely so for typical summer non-tidal river cruising. A larger engine (say 42HP) may stop the boat a little faster.On further point that you do not mention but in my view the engine power is one of the last things you need to worry about. For all new live-aboards the thing that causes most of them the most problems is keeping the batteries well charged, especially if you work full time unless you get a mooring with a mains power supply. Then recharging is easy. Start another topic if you need more information about the problems with battery charging.

quark3364
quark3364

Posted: Wed Aug 07, 2019 7:35pm

Post Subject: Engine size for river cruising

Thanks for your reply and knowledge shared found it informative

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