What size engine?

[Sy-Revolution]

...In HP would be ideal for a 70ft narrow boat?

Cheers,

C.

 

[vandy]

35+hp if Diesel Inboard.

a 70ft Narrow boat however will find it difficult to cruise especially against strong current if it has anything below 40hp Inboard.

If you plan to have an outboard, go above 100hp. outboard engines do not give enough torque which you need for a long narrow boat. Avoid outboard.

 

[cereal tiller]

50 bhp would be more than adequate,a bit of extra power is handy for manoevering.

modern narrowboats have a hull design which discourages speeds in excess of 5 miles per hour.

a larger engine would not be working efficiently at canal speeds.

 

[TrueBlue]

50 bhp would be more than adequate,a bit of extra power is handy for manoevering.

modern narrowboats have a hull design which discourages speeds in excess of 5 miles per hour.

a larger engine would not be working efficiently at canal speeds.

Echo that.
For use on rivers with a "reasonable" flow conditions 50hp will give that extra bit of grunt.

If you are not going to be on the Thames (or the Trent), then 43 would probably be sufficient.

I put a Beta 2203 in mine as we thought we might go on the French canals, but it's a bit overpowered for the Thames except on Red boards when it certainly has bee useful. 'cos it's a diesel I don't see much increase in consumption.

Remember that you won't ever use the 50hp. I cruise at 1600 rpm which is probably about 20hp. That's why a vintage type engine - RN, Lister, Gardner rated at 12HP upwards is viable as you would be using it towards the top of its output range.

 

[No Regrets]

Something weighing in at around four tonnes, enough to sink the horrible thing, would be ideal.

Then you can get a Boat...

 

[Sy-Revolution]

Thanks for the replies

 

[CJL]

I think you'll find you need more than that.

Take a pretty typical inflatable........this one has been fitted with a conservative 225hp and the owner complains its not quite fast enough.

 

[No Regrets]

Seriously though, my mates 70 foot NB has a 60hp, and it's a tad slow. The nice thing about a larger unit is you use it at lower revs, so it might be quieter!

 

[sturmvogel190a]

Torque the engine makes and prop size can be as important as hp ,narrow boats aint made for speed
More power than less is better as stated Steve

 

[dash300]

Seriously though, my mates 70 foot NB has a 60hp, and it's a tad slow. The nice thing about a larger unit is you use it at lower revs, so it might be quieter!

True it may be quieter, but a diesel run lightly stands more chance of bores glazing and wearing out prematurely. Those who run their engines off load for hours on end heating and charging are doing their engines no favours. I have a twin engine set up and the engine which runs the calorifier has significantly less compression and uses more oil than the other as a result of too much off load useage. Worth bearing in mind! The irony is, a diesel working hard is a happy diesel.

 

[Sy-Revolution]

The last two boats I've enquired about, a 70 and a 64 foot have both had 20hp engines. Are they seriously underpowered?

C.

 

[sturmvogel190a]

We have a BMC 1800 in our NB and think it is rated at 35hp ,If the engines you mention at 20hp are old fire every lamp post ones then the size of flywheel and torque generated can help offset any hp loss to some degree .
A good tip regardless of engine type is to have a second altenator fitted if poss so one charges starter battery and one the lesuire bank .

 

[No Regrets]

The last two boats I've enquired about, a 70 and a 64 foot have both had 20hp engines. Are they seriously underpowered?

C.

Not for the canals, but try punching the tide up the tidal Thames, and you'll be a sore loser!!

Engine size depends upon the planned usage, and desired resale value.

That would favour more than 20hp.

Our Broom 30 will nudge 8 and a bit knots on the Perkins 4108 (60hp) but amazingly 5knots on the 11hp Nanni Wing engine.

the Nanni would fail at the first whiff of a tide though, while the Perkins manages it fine, and that 60hp is needed!

 

[TQA]

Woow must be

" ported and relieved and stroked and bored "

cos most only manage 51 hp

[Perkins anorak ]

 

[My She]

Something weighing in at around four tonnes, enough to sink the horrible thing, would be ideal.

Then you can get a Boat...

Behave!

 

[No Regrets]

The 4108 appears to have a few variations in power according to the usage?!

I have read various claims from 30/35, on to 48 to 60bhp, mostly around 50-55 though. Given the Brooms unsporting hull, and fair weight (Around 6 tonnes in running order?) it would suggest more than 50hp would be required to give that sort of performance (if thats what you can loosely term 'performance...lol)

Doesn't seem too OTT for a 1.8 Diesel does it?

 

[rib]

4.108= 48 hp max

 

[sailorman]

The 4108 appears to have a few variations in power according to the usage?!

I have read various claims from 30/35, on to 48 to 60bhp, mostly around 50-55 though. Given the Brooms unsporting hull, and fair weight (Around 6 tonnes in running order?) it would suggest more than 50hp would be required to give that sort of performance (if thats what you can loosely term 'performance...lol)

Doesn't seem too OTT for a 1.8 Diesel does it?

it all depends on the RPMs used. it will rev to 4000.
i recon the one i had( low line ) @ 2900 max rpm was giving around 38hp.
it was replaced with a Nanni 4150 1500cc 37.5hp @ 3000rpm & i had to coarsen the MaxProp to get the revs to 2800 /2900

 

[rib]

about right 4,000 rev =48 ish and commercial use 3,000 rev =37 ish,but not 60 i belive

 

[Ramage]

The BMC 2.5 diesel aka Thorneycroft 154 is quoted as 50bhp @ 3000 rpm.