Bukh 36 - experiences?

[Guest]

Evening all

 

Does anyone have hands on experience with this engine in a canal narrowboat? If so I'd appreciate some feedback regarding daily use, also for gearbox model & prop combinations.

 

Much obliged

[mrsmelly]

Evening all

 

Does anyone have hands on experience with this engine in a canal narrowboat? If so I'd appreciate some feedback regarding daily use, also for gearbox model & prop combinations.

 

Much obliged

 

Hi

 

I owned a 65foot colecraft for a few years with one fitted. A first class in every way PROPER purpose built bullet proof marine engine. Started instantly at any temperature. Slightly smokey on tickover in locks against newer stuff but simply theeee best if you can get one which is why they are very expensive new.

I would have another without any hesitation whatsoever. I think Tony Brooks has one and he knows his stuff but then again I may be dreaming it.

Buy it. I think mine had a velvet drive box and it had a 17 by 11 prop.

 

Tim

[Guest]

Thanks for the feedback Tim

 

I'm doing this all the wrong way round, of course, I've bought the engine already (used but well loved, easy life yachting) with two gearboxes, the mid and the high ratio - both of which have a 2.5:1 ratio in reverse. Your prop was smaller than I'd imagined, but the boat was longer and heavier so I guess it adds up. I'm hoping for an Axiom 20", maybe even a 21"... we'll see how the numbers crunch through

[mrsmelly]

Thanks for the feedback Tim

 

I'm doing this all the wrong way round, of course, I've bought the engine already (used but well loved, easy life yachting) with two gearboxes, the mid and the high ratio - both of which have a 2.5:1 ratio in reverse. Your prop was smaller than I'd imagined, but the boat was longer and heavier so I guess it adds up. I'm hoping for an Axiom 20", maybe even a 21"... we'll see how the numbers crunch through

 

Hi

 

When I bought the boat it had a smaller still prop but I fitted the 17 which lowered the revs a little which was fine, the box was 2 to 1.

The engine was fitted new in 81 and I hear it is still on the same boat tho I havnt owned it for several years.

A brilliant piece of kit and of course proper marine stuff which is very rare on narrowboats. Good luck finding a boat to suit it.

 

Tim

[Tony Brooks]

I have a DV36 in a 54ft x hire narrowboat. About 12 years in hire and the rest with us as a weekend/holiday boat. It seems to have marginally more torque than a BMC 1.5 which is of a similar capacity. After 25 years it is still not burning a significant amount of oil but as is common with small direct injected engines it tends to smoke a bit at idle and low speed. t is very smooth for a three cylinder because it has internal balance weights and being a 3 it is short enough to allow the fitting of an Aquadrive in most cases. I would definitely advise that you do this otherwise you will be wasting the efforts put into making it smooth running.

 

We have taken it up the tidal Trent, down through London and in yellow/red flood boards on the Thames. I have not found it short on power. It was over-propped when we bought it which made the smoking worse. Crowthers specified and supplied a 16 x 14 (I think) prop. Being a modern boat we only have a 20" stern post so can not swing anything much larger.

 

Mine has a 2.5:1 mechanical gearbox as supplied b Bukh and made by a Spanish subsidiary of ZF. It has always tended to clonk into gear rather more than I would have liked but it is fine. That box is supposed to use mono-grade engine oil but after a short discussion with TW Marine (the "inland" Bukh agents) I now use red ATF so the family do not top the box up with multi-grade engine oil.

 

All in all I am very happy with the whole setup, a near hospital sized silencer I had fitted about 123 years ago makes the whole insulation very quiet. The only downside, if you can call it that, is that mine is a direct raw water cooled engine coupled to a skin tank so I have to service the rubber impeller Jabsco raw water pump every couple of years.

[WotEver]

... a near hospital sized silencer I had fitted about 123 years ago makes the whole insulation very quiet...

Around 1893 then, Tony? ?

[Tony Brooks]

Around 1893 then, Tony?

 

Not seen the white beard then?

 

Should be 12 to 13

[WotEver]

Venerable old man of The Thames ?

[Michael Siggers]

On 10/01/2016 at 09:39, Tony Brooks said:

It was over-propped when we bought it which made the smoking worse.

Hi @Tony Brooks

 

Very late to this discussion so I do apologies. I have posted before on a thread I created about my DV36 and engine revs when in gear.

 

I am due to check my prop, (kicking myself that I didn't when the boat was surveyed), but I think mine has been over propped as the maximum RPM when in gear is about 1500. Another oddity is that when in neutral it only idles at around 400 - 500rpm. Your thoughts would be greatly appreciated. When yours was over propped, did it lower the RPM of the engine when in gear?

 

Kind regards

 

Mike

[Tony Brooks]

45 minutes ago, Michael Siggers said:

Hi @Tony Brooks

 

Very late to this discussion so I do apologies. I have posted before on a thread I created about my DV36 and engine revs when in gear.

 

I am due to check my prop, (kicking myself that I didn't when the boat was surveyed), but I think mine has been over propped as the maximum RPM when in gear is about 1500. Another oddity is that when in neutral it only idles at around 400 - 500rpm. Your thoughts would be greatly appreciated. When yours was over propped, did it lower the RPM of the engine when in gear?

 

Kind regards

 

Mike

 

To try to keep thing simple. On a diesel, the only thing over propping should limit rev wise is the maximum revs the engine will reach in gear. The exact number relates to the degree of over propping, the more over propped the lower the maximum revs in gear. I don't see how it can affect the idle speed in neutral.

 

I gave my engine workshop manual away with the boat, so can't check the recommended idle speed, but sub 500 rpm seems a bit low to me. However, if it does not shake about in neutral or in gear it is probably OK, the flywheel is very heavy compared with automotive units so that helps give a smoother idle, even on a three pot.

[Michael Siggers]

2 minutes ago, Tony Brooks said:

To try to keep thing simple. On a diesel, the only thing over propping should limit rev wise is the maximum revs the engine will reach in gear. The exact number relates to the degree of over propping, the more over propped the lower the maximum revs in gear. I don't see how it can affect the idle speed in neutral.

Thank you @Tony Brooks

 

That makes perfect sense to me. I have the manual and it states 800 - 1000RPM for idle. However, I'm thinking if it was set to this, then when in gear 'tick over' would be really fast in terms of speed on the water? In other words, maybe the idle speed has been reduced to allow for the larger prop and when in 'tick over' speed? Although, I am now confusing myself more, so need to go and start the engine and see what RPM it is doing when the lever is in 'tickover' position.

 

Mike

[IanD]

2 minutes ago, Michael Siggers said:

Thank you @Tony Brooks

 

That makes perfect sense to me. I have the manual and it states 800 - 1000RPM for idle. However, I'm thinking if it was set to this, then when in gear 'tick over' would be really fast in terms of speed on the water? In other words, maybe the idle speed has been reduced to allow for the larger prop and when in 'tick over' speed? Although, I am now confusing myself more, so need to go and start the engine and see what RPM it is doing when the lever is in 'tickover' position.

 

Mike

If it'll only do 1500rpm flat-out that suggests it's heavily overpropped, the DV36 is rated at 35hp continuous at 3600rpm, output at 1500rpm is only 19hp.

[Michael Siggers]

Looks like it's arm down the weed hatch to measure the prop

 

Mike

[ditchcrawler]

34 minutes ago, Tony Brooks said:

 

To try to keep thing simple. On a diesel, the only thing over propping should limit rev wise is the maximum revs the engine will reach in gear. The exact number relates to the degree of over propping, the more over propped the lower the maximum revs in gear. I don't see how it can affect the idle speed in neutral.

 

I gave my engine workshop manual away with the boat, so can't check the recommended idle speed, but sub 500 rpm seems a bit low to me. However, if it does not shake about in neutral or in gear it is probably OK, the flywheel is very heavy compared with automotive units so that helps give a smoother idle, even on a three pot.

If both the idle and the maximum revs are low maybe the taco is out

[IanD]

1 minute ago, ditchcrawler said:

If both the idle and the maximum revs are low maybe the taco is out

Maybe by exactly a factor of 2?

 

(number of alternator poles set wrongly?)

[Tony Brooks]

46 minutes ago, Michael Siggers said:

Thank you @Tony Brooks

 

That makes perfect sense to me. I have the manual and it states 800 - 1000RPM for idle. However, I'm thinking if it was set to this, then when in gear 'tick over' would be really fast in terms of speed on the water? In other words, maybe the idle speed has been reduced to allow for the larger prop and when in 'tick over' speed? Although, I am now confusing myself more, so need to go and start the engine and see what RPM it is doing when the lever is in 'tickover' position.

 

Mike

 

I don't doubt the manual, but I agree, it sounds high for UK canal use. I am sure I had mine set at about 600 to 700 rpm and I know the rencounter was correctly set up because I did it against a hand held one.

[ditchcrawler]

I think I would check the actual engine speed with a hand held Taco.

[IanD]

2 minutes ago, ditchcrawler said:

I think I would check the actual engine speed with a hand held Taco.

How?

 

Edited January 29 by IanD

[Tony Brooks]

7 minutes ago, ditchcrawler said:

I think I would check the actual engine speed with a hand held Taco.

 

If the OP is any good with the forum search function I masure there ae posts describing how to use a cheap cycle computer to measure engine sped, and most phones seem to have a tacho ap these days

[Michael Siggers]

31 minutes ago, Tony Brooks said:

If the OP is any good with the forum search function I masure there ae posts describing how to use a cheap cycle computer to measure engine sped, and most phones seem to have a tacho ap these days

One arriving tomorrow.

 

So plan is;

1. Check actual engine speed and see how accurate the Tacho is
2. Measure the Prop as best as I can through the weedhatch,
3. Find Gearbox reduction Ratio

Long conversation with TW Marine, who were very helpful, and I can get the above information to him. Then form a plan of what to do.

 

Do seem to get some mixed messages though in terms of, some people say they have over propped and its ok as it reduces the revs etc, and TW Marine saying it's no good for the engine. On the post I created before, one person said they had deliberately added a larger prop to reduce the engine revs and it suited them for the Canals. TW Marine say the engine should go to over 3000 RPM when in gear, but this seems like it would be 'screaming'. Even say, 2500RPM when cruising would seem 'excessive/noisy' etc.

 

Mike

1 hour ago, IanD said:

If it'll only do 1500rpm flat-out that suggests it's heavily overpropped, the DV36 is rated at 35hp continuous at 3600rpm, output at 1500rpm is only 19hp

But at 1500 RPM, it is flying along, probably too fast.

[IanD]

1 minute ago, Michael Siggers said:

One arriving tomorrow.

 

So plan is;

1. Check actual engine speed and see how accurate the Tacho is
2. Measure the Prop as best as I can through the weedhatch,
3. Find Gearbox reduction Ratio

Long conversation with TW Marine, who were very helpful, and I can get the above information to him. Then form a plan of what to do.

 

Do seem to get some mixed messages though in terms of, some people say they have over propped and its ok as it reduces the revs etc, and TW Marine saying it's no good for the engine. On the post I created before, one person said they had deliberately added a larger prop to reduce the engine revs and it suited them for the Canals. TW Marine say the engine should go to over 3000 RPM when in gear, but this seems like it would be 'screaming'. Even say, 2500RPM when cruising would seem 'excessive/noisy' etc.

 

Mike

But at 1500 RPM, it is flying along, probably too fast.

 

There's nothing wrong with some overpropping to keep rpm and noise down but 1500rpm flat-out for a Bukh 36 seems pretty extreme -- and you then can get the problem that even at tickover the boat goes too fast, because there's not a big enough rpm difference between tickover and flat out. Unless tickover is set *very* slow, and that's not always good for the engine... 😞

[Michael Siggers]

6 minutes ago, IanD said:

Unless tickover is set *very* slow, and that's not always good for the engine... 😞

This may explain why the idle speed is slower than it should or could be?

[Tony Brooks]

7 minutes ago, IanD said:

 

There's nothing wrong with some overpropping to keep rpm and noise down but 1500rpm flat-out for a Bukh 36 seems pretty extreme -- and you then can get the problem that even at tickover the boat goes too fast, because there's not a big enough rpm difference between tickover and flat out. Unless tickover is set *very* slow, and that's not always good for the engine... 😞

 

And that may explain the low idle speed.

[Michael Siggers]

This is making sense now. (I've been having a slow day  )

 

Trying to find someone experienced with these engines near me is proving difficult.

 

Mike

[Alan de Enfield]

Just now, Michael Siggers said:

This is making sense now. (I've been having a slow day  )

 

Trying to find someone experienced with these engines near me is proving difficult.

 

Mike

 

They were used in Lifeboats so maybe try and find a service centre on the coast (maybe Aberdeen, or Lowestoft) where these life boats are tested.