What did you replace your Bukh DV20 with?

[Tranona]

Traditional Bukh is a great piece of engine, and now - as far as I know - the only real marine engine still produced. I mean the Bukh DV (you can also buy Bukh-Beta (kubota) which is not).
Why change for inferior, when you have already boat set for one? Shaft, gears - cost some.

Purchasing new DV, 24 HP is costly (and worth it ), but it was possible to exchange old for factory refurnished one (as good as new) for much less then buying even cheapest new engine. I heard something around 3-4000 euro, but not sure. Worth to ask I think.
Rebuilding one in Germany (not in factory but at dealer service) I was quoted about 2000 euro, more if some problems arise. But from factory you will get everything done anew. Rebuild at mechanic may leave some issues, you never know.

Talk with Bukh company directly, not the distributors, especially in UK - my tip .
http://www.bukh.dk/dv24rme/
.
They are much better then new Kubotas (Beta) or Perkins (Volvo) and deliver real power - btw don't be misled by HP rating , as high-revving engines can be rated high HP - at 4000 revs, but would you use this? Even if so, prop will not probably deliver. I would say IMHO that for 20 HP bukh you should take at least 25 hp kubota to match performance at sea, that is against some resistance - or indeed invest in a better prop, as mentioned .
Only drawback of Bukh I know is raw water cooling, (it has a merit of simplicity though) - but that can be simply changed to indirect, no problem.

Are you saying that nothing has changed over the last 40 years or so? The Bukh has its good points - and makes a good engine for a lifeboat which is rarely used and simplicity is valued.

However, sailing boats have moved on. They are now warm and dry inside, have plenty of battery power, are smooth and refined. Owners want their engine to start and run smoothly and quietly as well as provided hot water on demand.

All this is possible with modern engines. Freshwater cooling allows the engine to run hotter and more efficiently and keeps the nasty hot seawater awway from the engine. The base engines used (mostly Japanese industrial diesels) will outlast most of the other equipment in the boat. 8000 hours is a typical life - given the typical leisure use of 150 hours a year that is over 50 years.

Just nonsense to say that a Bukh 20 hp engine is more powerful than a 25hp Kubota. If you hang around here long enough you will see (as in this post) people comment on the improved motoring performance and greater refinement they get when they replace old style engines with new ones. BTW the new engines don't rev to 4000 - 3600 is common, the latest Volvo Perkins is 3200 - and they are designed to run all day long at 3000+revs. Next time you go to a building site, look at the little diggers - they run all day, every day in conditions that make a yacht auxilliary look like luxury. My Volvo Perkins has run over 3500 hours from when I bought it new and runs just the same as it did when new 12 years ago.

This is not intended to knock Bukh - it is a fine bit of kit - just not the best thing for a modern yacht auxilliary.

 

[VicS]

BTW the new engines don't rev to 4000 - 3600 is common,

See http://www.betamarine.co.uk/seagoing/seagoing_engines.html

 

[snooks]

See http://www.betamarine.co.uk/seagoing/seagoing_engines.html

As Tranona said. The modern engines don't rev to 4,000. 3,600 is more common

 

[30boat]

Are you saying that nothing has changed over the last 40 years or so? The Bukh has its good points - and makes a good engine for a lifeboat which is rarely used and simplicity is valued.

However, sailing boats have moved on. They are now warm and dry inside, have plenty of battery power, are smooth and refined. Owners want their engine to start and run smoothly and quietly as well as provided hot water on demand.

All this is possible with modern engines. Freshwater cooling allows the engine to run hotter and more efficiently and keeps the nasty hot seawater awway from the engine. The base engines used (mostly Japanese industrial diesels) will outlast most of the other equipment in the boat. 8000 hours is a typical life - given the typical leisure use of 150 hours a year that is over 50 years.

Just nonsense to say that a Bukh 20 hp engine is more powerful than a 25hp Kubota. If you hang around here long enough you will see (as in this post) people comment on the improved motoring performance and greater refinement they get when they replace old style engines with new ones. BTW the new engines don't rev to 4000 - 3600 is common, the latest Volvo Perkins is 3200 - and they are designed to run all day long at 3000+revs. Next time you go to a building site, look at the little diggers - they run all day, every day in conditions that make a yacht auxilliary look like luxury. My Volvo Perkins has run over 3500 hours from when I bought it new and runs just the same as it did when new 12 years ago.

This is not intended to knock Bukh - it is a fine bit of kit - just not the best thing for a modern yacht auxilliary.

Ah some sensible words at last.IMO the Bukh is as outdated as they come and a 20plus year old one will be prone to leaking and other assorted problems.Yes they can be made to last but at a huge cost.I know of at least three boats (mine included) that had their Bukhs replaced with Betas and all three owners are very happy with the new engines.My old Bukh now 30 years old is still being used in another yacht but I'm sure it's not trouble or leak free.

 

[vyv_cox]

I replaced my Bukh 20 with a Yanmar GM30F (27 HP) about ten years ago. It is 100 kg lighter, far smaller and a lot more powerful. Not to mention smoother. The only changes made were to add bearer plates one inch thick, increase the size of water supply and exhaust hoses and a few other small changes. Our Bukh was not clapped out but showing its age despite having had a partial recon a couple of years earlier. It was particularly rattly, maybe the chain to the hand starter, which was impossible to use anyway. Preparing to live aboard for the future a change was justified. Best thing we could have done, the Bukh IMHO is yesterday's technology, now superseded by far superior engineering.

 

[Blueboatman]

Reluctantly I would have to agree with you. Current same Yanmar v nice-mostly-but I do carry a spare starter motor and a genny cos handstart is not an option.

I once had a 'real marine engine', a Sabb. 8hp @400 lb weight but v easy to hand start, no waterpump impellor, variable/feathering prop, greasers and grease nipple for the top end instead of an oil pump(!) etc. But it was v v noisy after 20 minutes.

 

[Tranona]

I have no obligation to write here if You do not want me to, as already said elsewhere.
Done Academy on them, but then You probably know everything better

Sorry if that is what you think, but what you are saying is very misleading - and your example just illustrates it. Comparing one engine that maxs at 3000 and produces 20 with another that produces 20hp at 3000 but is rated to 3600 when it produces 25 hp and then claim the former is "more powerful" is clearly wrong.

A sailing boat auxilliary is virtually a constant speed engine - you choose the revs to give the power to produce the speed you want. The speed on a displacement hull is limited by its length and the horsepower required to achieve that speed for any given length is largely a function of weight - the heavier the boat, the more power required. However, what converts that power into motion is the propeller, and the shaft speed is critical to obtain the maximum speed from the power of the engine. It does not care what engine is providing the power, shaft speed is determined by the reduction ratio in the gearbox.

Larger diameter props need lower shaft speeds, so were common when engine speeds were lower. However many modern boats with flat hulls cannot swing large props and keep shaft angles within tolerance, so tend to use smaller diameter coarser pitched props which run at higher shaft speeds. Many manufacturers offer alternative gearbox ratios to allow different sizes of props to cater for boats that can use larger props - one of my boats had a 9hp Yanmar - but a 15" prop on a 3.1:1 gearbox because it was a heavy boat with a long wide keel, so the bigger the prop the better. The same engine is also available with a 2:1 box and is commonly used in light boats with small higher speed props.

The "new" style engines (not so new, been around for over 30 years) are ideal for this application. They have linear power curves - the faster you rev them the more power they produce, flat torque curves so are fuel efficient over a wide range and are relatively lightly stressed (that is low specific power output). Properly sized for the boat and fitted with the correct propeller they will achieve maximum hull speed at maximum revs and cruise at a comfortable speed at revs equivalent to around 70% of maximum power, leaving ample reserves for adverse conditions. So my 29hp Volvo achieves over 7knots at 3600 and cruises at 5.5knots at 2500 using 20hp.

Yacht auxilliares do not usually wear out. As I noted earlier the design life is over 8000 hours. They don't like neglect, running slowly for long periods and the bits that fail are usually the ones than come into contact with salt water such as heat exchangers, water pumps and exhausts.

You can argue that older, heavier lower revving engines are better, but as you will see from posts here, this is not necessarily true in practice. Engines from the 1970's and 80's are coming to the end of their life and although technically it is possible to rebuild them, it is often not economic and you still end up with an old engine that is just not as refined as a new one.

 

[stav]

Can ancillaries such as injector pumps be dropped of the modern Kubota engines and be rebuilt? If ever I had to put a new engine in that would be my question can it be serviced for its lifetime or will it run sweetly for 8000 hours and then just disintigrate? And by serviced I mean pump, injectors, ease of cleaning the heatexchanger, glow plugs, head gasket etc not just pouring new oil in.

 

[reeac]

Rossynant: I looked at your curves for Bukh and Beta and, in order to get a better comparison, I read off some torque/rpm data. The simplest conclusion is that the two engines exceed 50Nm. torque as follows:
Bukh between 1200 and 3250 rpm. .. peak of 56 Nm. at 2000 rpm.
Beta between 1700 and 3400 rpm. ...peak of 57.5Nm. at 2500 rpm.

The above numbers support your comment that the Bukh has the flatter torque curve.

 

[Tranona]

Sorry I am also, Tranona, that was more for Vics - who tried to prove me wrong elsewhere in quite silly discussion. (You only a bit )

But then - why don't you read what I said, just putting other words in my mouth??? The text is above, you can check.

Don't want to get into an argument, but suggest you read back what you were trying to explain. Effectively you were just comparing power at certain revs to show that the Bukh is "more powerful". and you also said a 20hp Bukh would perform as well as a 25hp Kubota.

All I was trying to say is that is misleading. The propeller does not care where the HP comes from or a what rpm - it is the shaft speed that is important. So if you have to run the Kubota 500 rpm higher so what? that is what it is designed to do. You could go the other way - my old Stuart Turner 2 stroke (a "proper" marine engine) produced 8hp at 1200rpm with a direct drive gearbox. I replaced it with a Yanmar 1GM rated at 9 hp at 3600 rpm, but a 3.1:1 reduction and would happily run at 3000 all day long.

You can argue that a Bukh will last longer than a Kubota - but as you will see from many posts here, this is not borne out in practice. The engine was better than its competitors 30 years ago, which is why it became popular - however, many are being replaced after 30 years, even if they have been rebuilt during that time. On the other hand, I know of Yanmars on charter boats in the Med which have run well over 10000 hours with no problems. It is not running the engines that shortens their life - it is the typical duty cycle of a small yacht auxilliary which spends most of its life doing nothing and is used for short periods at a time.

As to rebuilding and reconditioning engines, this is a thing of the past. My brother made his fortune out of reconditioning engines from cars built in the 1960s to 1980s when there was a reconditioning shop in every major town and it was not unusual to need a new engine after only 40000 miles. This business has disappeared as engines now generally outlast the car.

It is much the same with small marine engines - things like hand start and easy to rebuild mechanics were valued in the past, because it was necessary, not because it was desirable. Things have moved on and there is less need for this sort of thing. We are lucky in the marine industry in that there is a huge market for small industrial engines so the volume is there to produce simple reliable engines that can be marinised for the low volume marine market. The result is smaller, lighter smoother - and cheaper.

 

[Vara]

Poor old Snooks, all he wanted was an engine recommendation, and got involved in a torquey bun fight.

My own researches for replacing my ancient Volvo 2003, seem to keep coming back to Beta as an option, mainly on the grounds that it is the easiest to fit.

On asking around there doesn't seem to be much between the two main contenders Beta/Nanni in terms of reliability or cost.

However you cut it, it's arm and two legs time.

 

[Tranona]

Poor old Snooks, all he wanted was an engine recommendation, and got involved in a torquey bun fight.

My own researches for replacing my ancient Volvo 2003, seem to keep coming back to Beta as an option, mainly on the grounds that it is the easiest to fit.

On asking around there doesn't seem to be much between the two main contenders Beta/Nanni in terms of reliability or cost.

However you cut it, it's arm and two legs time.

Had the same dilemma when I replaced my Yanmar. There are minor (but some might say important) differences in the marinisation bits between the two, but not entirely sure it makes any real difference - but the Nanni is blue and co-ordinates better with the hull colour!

 

[snooks]

Poor old Snooks, all he wanted was an engine recommendation, and got involved in a torquey bun fight.

My own researches for replacing my ancient Volvo 2003, seem to keep coming back to Beta as an option, mainly on the grounds that it is the easiest to fit.

On asking around there doesn't seem to be much between the two main contenders Beta/Nanni in terms of reliability or cost.

It's looking like a Beta at the moment.

Why?

Well the choice has partly been taken out of my hands by the engine designs. While I could get the 30hp Nanni with a 100A alternator for roughly the same price of the Beta 25, however I don't think I'll be able to get to the dipstick very easily because it's near the back of the engine. Actually getting it out would be OK, but getting it back in......hmmmmm

So it look like a Beta for the following reasons:

• Good comments on the kind peeps on the forum
• All the service are at the front or on top (essential for the access I have)
• The exhaust can be crossed over
• Can be fitted onto the existing Bukh DV20 foot print
• Dipstick is accessible from the front
• Within budget (ish)

But it then comes to whether to go for the 20 or 25 and get the 70A alternator or the 30 with the 100A alternator

 

[snooks]

but the Nanni is blue and co-ordinates better with the hull colour!

I think Pixie has been used to a red engine for so long, getting another colour might confuse the old girl

 

[Mistroma]

Apologies if I've missed this point but I don't have time to read the whole thread this morning.

I seem to remember that the BUKH DV 20 actually gave 20HP at the shaft and so output at flywheel might have been more like 23HP. I had the full workshop manual so may have read that there. I think other manufacturers might quote power at flywheel (i.e. before gearbox losses).

Don't know if that helps Snooks decide between options available now. Perhaps someone else will confirm this point.

I had a BUKH DV 20 for around 23 years and still going strong as far as I know at over 30 years age. Great engine but I heard that there were problems with head gasket on those built in early 80s. I changed the gasket as soon as I bought Mistroma (just in case), perhaps that was one reason my Bukh never gave cyl. head problems. Must have covered at least 17,000 miles during that time so plenty of opportunity to find faults.

 

[VicS]

Apologies if I've missed this point but I don't have time to read the whole thread this morning.

I seem to remember that the BUKH DV 20 actually gave 20HP at the shaft and so output at flywheel might have been more like 23HP. I had the full workshop manual so may have read that there. I think other manufacturers might quote power at flywheel (i.e. before gearbox losses).

Don't know if that helps Snooks decide between options available now. Perhaps someone else will confirm this point.

I had a BUKH DV 20 for around 23 years and still going strong as far as I know at over 30 years age. Great engine but I heard that there were problems with head gasket on those built in early 80s. I changed the gasket as soon as I bought Mistroma (just in case), perhaps that was one reason my Bukh never gave cyl. head problems. Must have covered at least 17,000 miles during that time so plenty of opportunity to find faults.

I think you will find that the method of quoting engine power changed in the 1980s generally from quoting crankshaft power to quoting propshaft power, at least where the engine and gearbox are sold as a complete unit

It is detailed in ICOMIA 28-83.

The only link I have refers to outboards but the standard applies to inboards as well.
http://continuouswave.com/whaler/reference/ICOMIA28-83.html


.

 

[snooks]

I've just noticed Rossynant has deleted all their posts

Strange, being a mod I can still read them, which is good because any view point is interesting to read, but it's a shame for anyone else reading this thread at a later date because they don't get to benefit from Rossynant's opinions.

 

[VicS]

I've just noticed Rossynant has deleted all their posts

Strange, being a mod I can still read them, which is good because any view point is interesting to read, but it's a shame for anyone else reading this thread at a later date because they don't get to benefit from Rossynant's opinions.

Not only on this topic but all his posts on all topics to which he had contributed.

A some of the content preserved as quotes though.

 

[robmcg]

It's looking like a Beta at the moment.

Why?

Well the choice has partly been taken out of my hands by the engine designs. While I could get the 30hp Nanni with a 100A alternator for roughly the same price of the Beta 25, however I don't think I'll be able to get to the dipstick very easily because it's near the back of the engine. Actually getting it out would be OK, but getting it back in......hmmmmm

So it look like a Beta for the following reasons:

• Good comments on the kind peeps on the forum
• All the service are at the front or on top (essential for the access I have)
• The exhaust can be crossed over
• Can be fitted onto the existing Bukh DV20 foot print
• Dipstick is accessible from the front
• Within budget (ish)

But it then comes to whether to go for the 20 or 25 and get the 70A alternator or the 30 with the 100A alternator

Just make sure you get a Beta with the poly-vee belt system, not the standard alternator belt which can make the unsupported pipe from the raw water impellor to the heat exchanger vulnerable if you have to change the belt whilst at sea. Pointed this out to Beta who were a bit sheepish and suggested a poly-vee conversion. Standard 70A alternator has been fine for charging our 320A house batteries.

Rob (with a 2003 Beta 38)

 

[30boat]

One thing I noticed on my friends Fulmar that now has a 25hp Beta is that with the Autoprop there's a marked tendency to squat at full power.Snooks boat having a narrower stern than a Fulmar would be even more prone to this so maybe a 20hp would be more than enough .And cheaper too.