Engine size advice

[Great Escape]

Hi all 

So we’re having a 59’ x 11’ widebeam built and as standard it comes with a Canaline 52 hp engine, I am being advised that I should upgrade to the 60 engine at a cost of £2.5k (Not by the builder) for £3k I could get the Canaline 70hp. My issue is on doing some research it turns out the 60 is only 5hp more than the 52 (57hp) so my questions are..

 

 

1. Would 5hp really make that much difference (Occasionally going on tidal Trent) ?
2. If more hip is needed would it be worth going the 70 route (Which is actually 65hp) ?
3. Should I just save my 2.5-3k ?

 

I would very much appreciate your input

 

Thanks in advance

 

Edited August 19, 2021 by Great Escape
Typo

[matty40s]

If you are going to be using the tidal Trent, go for the biggest, as especially at Spring tide times, and in times of flood strong flows, you may well need a bit of extra oomph, just to get you out of a tight corner.

I'm not sure that the builder isnt trying to confuse you as your hp's and engine numbers seem to be a bit mixed up. 

[Great Escape]

1 minute ago, matty40s said:

If you are going to be using the tidal Trent, go for the biggest, as especially at Spring tide times, and in times of flood strong flows, you may well need a bit of extra oomph, just to get you out of a tight corner.

I'm not sure that the builder isnt trying to confuse you as your hp's and engine numbers seem to be a bit mixed up. 

Hi buddy 
Thanks for the reply

Boat builder has been fine tbh, not really tried to sway me in any way ,it’s just the way Canaline name/market their engines…

Canaline 52 = 52hp

Canaline 60 = 57hp

Canaline 70t = 65hp

 

[matty40s]

45 minutes ago, Great Escape said:

 

1. If more hip is needed would it be worth going the 70 route (Which is actually 55hp) 

 

 

Ah, that's better, above is wot confused me...

[Great Escape]

3 minutes ago, matty40s said:

Ah, that's better, above is wot confused me...

Doh , typo , sorry

[BEngo]

If and when  you need the extra power, finding you haven't got it is too late.   Go large.  You don't have to use full power every day and in the range you are talking about the fuel consumption will not be significantly different whatever you fit.

 

However, check that if you go bigger than standard the skin tanks or other cooling arrangements get enlarged to suit the bigger engine.  If you want to go all day on the Trent, or other rivers, the limiting factor can be the ability to cool the engine.  I expect you will need as a bare minimum somewhere between 13 square feet (52 hp) and 17 square feet (65hp) of skin tanks.  More if they are thicker than about an inch internally  or if they are not well baffled.  That probably means two tanks, one on each swim, piped in series. 

 

There is no such thing as too much cooling capacity.  The engine has a thermostat which will prevent over cooling and you need to be able to dump about as much heat as there is useful power coming out of the engine. So for, say, a 60bhp engine operating at full power, 45 kW goes into the cooling, 45  kW goes out the exhaust and as noise and 45 kW is delivered as power to the propeller, alternators etc.

 

N

 

 

 

 

[bizzard]

If there's room for a larger diameter prop I'd go for a 3.1 reduction gearbox. The widebeam boats I've steered for people with 2.1 boxes always seemed to cavitate the prop badly when starting off until the boat is well on the move, a horrible high pitched rushing noise that can damage the prop.

[MtB]

7 minutes ago, bizzard said:

If there's room for a larger diameter prop I'd go for a 3.1 reduction gearbox. The widebeam boats I've steered for people with 2.1 boxes always seemed to cavitate the prop badly when starting off until the boat is well on the move, a horrible high pitched rushing noise that can damage the prop.

 

I'd agree with this but bear in mind it (probably) A) also means a deeper swim, which may not be possible if the shell construction has already started, and B ) mean several tonnes more ballast to get the bigger diameter blade fully immersed in the water.

[TheBiscuits]

14 minutes ago, bizzard said:

The widebeam boats I've steered for people with 2.1 boxes always seemed to cavitate the prop badly when starting off until the boat is well on the move, a horrible high pitched rushing noise that can damage the prop.

 

Set off slower to allow the momentum to build then feed it more power.

 

There is a reason cruise liners or oil tankers don't hit full power before leaving the terminal ...

[dmr]

The counter argument is that diesels really hate light load running so the bigger the engine the lighter the load (relative to its maximum output).

For most boaters who only do a few hundred hours each year this probably does matter at all, but if you are going to put a huge numbers of hours on then it just might be a small factor.

[bizzard]

7 minutes ago, MtB said:

 

I'd agree with this but bear in mind it (probably) A) also means a deeper swim, which may not be possible if the shell construction has already started, and B ) mean several tonnes more ballast to get the bigger diameter blade fully immersed in the water.

I agree, but I did say ''if there's room''.

[dmr]

Just now, TheBiscuits said:

 

Set off slower to allow the momentum to build then feed it more power.

 

There is a reason cruise liners or oil tankers don't hit full power before leaving the terminal ...

 

This is very obvious. If I apply a lot of power at zero speed there is obvious significant turbulence at the water surface, as the boat progressively reaches its "prop" speed the water settles down till its just a neat little lump in the water.

[bizzard]

2 minutes ago, TheBiscuits said:

 

Set off slower to allow the momentum to build then feed it more power.

 

There is a reason cruise liners or oil tankers don't hit full power before leaving the terminal ...

The ones I've steered do it directly I've put them in gear. 

[TheBiscuits]

15 minutes ago, bizzard said:

The ones I've steered do it directly I've put them in gear. 

 

Numpty builders.  I have adjusted quite a few Morse levers to the other engage position, because going into gear at lower revs makes a huge difference especially on bigger boats.

 

I have had several people who were concerned their "tickover" speed was too fast think I am a genius because I moved the pin one hole.  It's one of my pet hates!

 

 

 

Edited August 19, 2021 by TheBiscuits
spellink

[Tony Brooks]

8 hours ago, TheBiscuits said:

 

Numpty builders.  I have adjusted quite a few Morse levers to the other engage position, because going into gear at lower revs makes a huge difference especially on bigger boats.

 

I have had several people who were concerned their "tickover" speed was too fast think I am a genius because I moved the pin one hole.  It's one of my pet hates!

 

 

 

 

That sounds as if the throttle cable was not fitted when the control was in slow ahead or reverse and the cable properly adjusted.. The hole position should make no difference to the idle speed because that is set by the idle stop screw and then cable length. Altering the throw on the lever (the different hole) should only make a difference to the achievable top speed, and only then if the engine lever does not run out of movement first.

[Jen-in-Wellies]

10 hours ago, BEngo said:

If and when  you need the extra power, finding you haven't got it is too late.   Go large.  You don't have to use full power every day and in the range you are talking about the fuel consumption will not be significantly different whatever you fit.

 

However, check that if you go bigger than standard the skin tanks or other cooling arrangements get enlarged to suit the bigger engine.  If you want to go all day on the Trent, or other rivers, the limiting factor can be the ability to cool the engine.  I expect you will need as a bare minimum somewhere between 13 square feet (52 hp) and 17 square feet (65hp) of skin tanks.  More if they are thicker than about an inch internally  or if they are not well baffled.  That probably means two tanks, one on each swim, piped in series. 

 

There is no such thing as too much cooling capacity.  The engine has a thermostat which will prevent over cooling and you need to be able to dump about as much heat as there is useful power coming out of the engine. So for, say, a 60bhp engine operating at full power, 45 kW goes into the cooling, 45  kW goes out the exhaust and as noise and 45 kW is delivered as power to the propeller, alternators etc.

 

N

 

 

 

 

Hi @Great Escape,

This above ^^^^^^^^. Something I forgot to mention when we were talking about this last weekend. I've come across several boats overheating on the tidal Trent from inadequate cooling. Peak power is useful. I can think of an instance getting in to Keadby against a strong tide, where I was making maybe 1/2mph progress after turning to stem the tide, prior to turning in to the lock. Definitely worth asking the builder the square footage (or metreage) of skin tank they intend to fit.

Jen

[dmr]

I'm feeling technical so.....

 

The difference between a 55 and and a 60Hp engine in terms of maximum boat speed (and hence river flow that you can cope with) is very small and might be zero.

The ultimate "power" and speed of boat depends upon both the engine and the prop.

Sometimes when a company offers a choice of engines with a small increase in power its actually the same engine, the "bigger" one might be rated to run to a slightly higher speed, it might even be the same.

 

If an engine and prop are well matched so that prop load matches engine torque at required maximum cruising speed then fitting an engine with the same torque curve but a higher max speed will achieve nothing because the engine will not reach that speed. Fitting a big engine and suitable bigger prop might result in a higher than desired boat speed at tickover.

 

Make sure that your boat builder understands all this and is not just fitting any engine that the customer specifies. Looking at the new boats going past I sometimes suspect that some (not all) builders just build boats and have never done any actual boating.

[MtB]

7 minutes ago, dmr said:

The difference between a 55 and and a 60Hp engine in terms of maximum boat speed (and hence river flow that you can cope with) is very small and might be zero.

The ultimate "power" and speed of boat depends upon both the engine and the prop.

 

Let's not overlook the hull either, or more specifically the ratio of waterline width to waterline length IIRC. Even if the (larger) engine is propped to transmit all the extra horses into the water, a point arrives when the hull is climbing its own bow wave and feeding in more revs just sucks more water from under the hull so the bow wave gets steeper/higher. Eventually with enough engine power the boat can climb over the bow wave and the boat starts planing.

 

And I don't think we want THAT to happen with a tiller-steered widebeam on the Trent, do we children? 

[TheBiscuits]

1 minute ago, MtB said:

I don't think we want THAT to happen with a tiller-steered widebeam on the Trent, do we children? 

 

Definitely not.  That's what the Oxford Canal is for ... 

[MtB]

1 minute ago, TheBiscuits said:

 

Definitely not.  That's what the Oxford Canal is for ... 

 

Nooooo.... on the Oxford the effect is completely different. 

 

If you feed in power, more water is sucked from under the boat and it sinks deeper into the silt and you go along slower.

 

DAMHIK. On some of the Napton locks I was actually grounding inside them when empty and with the boat in neutral the other day. 

 

 

[Great Escape]

12 hours ago, Jen-in-Wellies said:

Hi @Great Escape,

This above ^^^^^^^^. Something I forgot to mention when we were talking about this last weekend. I've come across several boats overheating on the tidal Trent from inadequate cooling. Peak power is useful. I can think of an instance getting in to Keadby against a strong tide, where I was making maybe 1/2mph progress after turning to stem the tide, prior to turning in to the lock. Definitely worth asking the builder the square footage (or metreage) of skin tank they intend to fit.

Jen

Thanks @Jen-in-Wellies