replacing my BUKH DV20

[alexander]

Dear LM-friends,
my BUKH DV20 engine on my LM 27 (from 1973) has to be replaced, cannot be repaired anymore, my mechanic says. Has anyone done that before? Is the BUKH DV24 the exactly matching successor engine of the DV20, as I have heard? Are there any known problems occurring when replacing the DV20 by a (new or used) DV24?
I would appreciate very much any suggestions or sharing experiences on the subject, thank you in advance, guys!
Alexander, Switzerland

[Sula]

Welcome to the Forum, Alexander.

It is most unlikely that a Bukh 20 cannot be repaired. They are simple, strongly built engines, and almost all the parts are readily available, if rather expensive.

Whether to repair/rebuild an old Bukh or replace it with another engine is a less clear cut question. This old thread on the YBW Forum discusses that question, and a interesting range of different views are given. (Note that the prices mentioned will no longer be valid.) forums.ybw.com/index.php?threads/replace-a-bukh-with-a-bukh-or-something-else.256568/

My understanding (in part from that thread mentioned above) is that the DV24 engine mounting is the same as the DV20, but that some earlier DV20s had a different gearbox to that used on both the later ones and the DV24, and the output shaft of the earlier gearbox is at a different height. If your current engine has the earlier gearbox then fitting the DV24 would be more complicated, and involve changing the engine mountings' height in the boat. Note that the DV24 is usually (perhaps always?) indirect (freshwater) cooled, so may add some advantages and complications to changing from what I assume is a direct (seawater) cooled DV20. You can download the installation drawing for the DV24, and other relevant documents, from here - bukh.dk/produkter/6-bukh-24-75hp-lifeboats/10-bukh-dv24-rme/

I believe the current cost of a new Bukh DV24 series engine is in the region of £8,000 - more expensive than other marine engines of similar power.

The advantage of changing to another Bukh is that it will avoid changing the engine mountings (unless you have the earlier gearbox), prop shaft, propellor, exhaust and inlet hoses, etc., etc, which will often be different sizes and/or positions to the Bukh and can add substantially to the cost of changing the engine. On the other hand, almost all other engines will be significantly lighter in weight than the Bukh!

Few people would remove a Bukh engine from a boat if it was in good condition and running well, so I would be wary of second hand engines, though you could get lucky. You may find companies selling 'refurbished' second-hand engines, but you need to be clear what they mean by 'refurbished' (it may be a substantial rebuild or perhaps nothing at all, or just cosmetic new paint!).

Because Bukhs are widely used on ships' lifeboats (their main market now), and these have to be serviced regularly and replaced at certain dates, one can find companies selling ex-lifeboat DV20s (and probably DV24s) which will typically have very low engine hours, even if they are some years old. I don't know if there are such companies in mainland Europe, but there is such a company in England (it is also a Bukh agent). I must emphasise I have no connection with this company, and no experience from which to judge the quality of their services. I see they currently have for sale used DV24s (ex-lifeboat?) for sale for around £2,500 - £3,000 and used DV20s (probably taken in part-exchange for lifeboat engines they have sold) for around £1,500 - £1,700. www.marineenterprises.co.uk/list-all-adverts///type/boat-engines-2/manufacturer/bukh-3?expanded=0

I hope you manage to get something sorted. Let us know how you get on.

[johnc]

If you decide a new engine is the way to go then perhaps you should talk to a UK company called Beta Marine who use kubota engies as their base unit. They have developed a tange of adapter feet which allow their engines to slot into existing engine bearers.

Here is a link to their web page which gives information on non standard engine brackets.

betamarine.co.uk/seagoing-special-feet/

[alexander]

Thanks Sula and Johnc for your thoughts!

I tried already to contact (through their website) Marine Enterprises during the last couple of days but they didn't reply until now. I think I will have to call!

I also learned in the meantime that the DV24 unfortunately isn't licensed for the lake of Constance where my boat is running, so it seems I will have to look for an older DV20 then.

And yes, that's what everybody told me until now, an old BUKH DV20 cannot be unrepairable... but my mechanic thinks there must be a hidden crack somewhere in the motor block because we don't have compression so we cannot start the engine anymore, and he tried out to repair and adjust anything else before to get it started again - without success. Also it seems that some water has got into the cylinders because there was some rust found within, therefore the idea of a crack somewhere in the motor block although we didn't see where it is.

I will let you know if I know more.
Alexander

[Sula]

I have to say I am a bit sceptical of your engineer's diagnosis. I am no engineer, but the the Bukh has cylinder liners, so I struggle to see how a crack in the motor block would cause lack of compression.

I am also curious as to how this could cause loss of compression in both cylinders. If you had a crack in a cylinder (and a liner would, I think, be much less liable to cracking than a cast block) you would still be able to start the engine on one cylinder. The chances of a crack occurring in both cylinders at the same time seems to me extremely unlikely.

As far as I can think, a new loss of compression in both cylinders at the same time could perhaps be (a) piston rings stuck after a long period out of use, or due to ingress of water; (b) head gasket failed between the two cylinders; (b)valves not seating because the rocker cover has been incorrectly replaced*, decompressor lever stuck in the wrong position, tappets incorrectly adjusted, or rust on the valve seats or stems; (c) a crack between the two cylinders in the cylinder head; or (d) cylinder head not properly tightened down.

*I seem to remember someone had a problem with a Bukh 20 which turned out to simply be the rocker cover had been tightened down too hard, which compressed the rocker cover gasket, and resulted in something (decompressor?) holding the valves slightly open. In the course of investigating the problem he found that not all the gasket on sale were the same thickness. I can't remeber the exact details but will try to find the thread later in case it is of any help to you.

As I say, i am no expert on this, and though I've done a fair bit of messing with engines they were mainly petrol motorcycle ones, I may be wrong about any of the above.

In any case, as I said before, even if it can be repaired, whether you do that or get a replacement engine is another question. It's one only you can decide.

John C mentioned Beta engines. I had one in a previous boat and was very pleased with it. Beta Marine are well known here for their excellent after-sales support, and prices may be attractive for a foreigner currently, as the pound sterling is rather weak.

Good luck.

[alexander]

Thanks again, Sula!

My plans to purchase one of the older used BUKH DV20 from Marine Enterprises in Dorchester failed because Sean, the manager, just wrote me back this morning that he hasn't any of them anymore in stock (but they are still on his website...).

The technical questions you bring up in your last post I will discuss with my engineer once more, I am also a bit sceptical, but he tried to fix the engine in many ways (but since three months never managed to get it started) - so he ended up with his guess there could be a crack in the motor block as reason for cooling water entering into one of the cylinders where he found some rust (as much as I understood). The lacking compression is mainly in one of the two cylinders, and also my father (who used to be an engineer himself and worked on this DV20 engine for 40 years himself as long as the boat was his own property!) thinks that the engine should still start on one of the cylinders, exactly as you wrote it yourself.
At the moment I am a bit helpless on how to go on...

To be continued!

[johnc]

Aug 18, 2020 16:32:36 GMT alexander said:

Thanks Sula and Johnc for your thoughts!

I tried already to contact (through their website) Marine Enterprises during the last couple of days but they didn't reply until now. I think I will have to call!

I also learned in the meantime that the DV24 unfortunately isn't licensed for the lake of Constance where my boat is running, so it seems I will have to look for an older DV20 then.

And yes, that's what everybody told me until now, an old BUKH DV20 cannot be unrepairable... but my mechanic thinks there must be a hidden crack somewhere in the motor block because we don't have compression so we cannot start the engine anymore, and he tried out to repair and adjust anything else before to get it started again - without success. Also it seems that some water has got into the cylinders because there was some rust found within, therefore the idea of a crack somewhere in the motor block although we didn't see where it is.

I will let you know if I know more.
Alexander



The issue with water in the engine may not be due to a crack but may be coming back down the exhaust as the engine will be drawing lake water into the engine all the time the mechanic is trying to start the engine.   It is usually advised to close the seacock while trying to start a  difficult engine and open it as soon as the engine starts.

[Sula]

I agree, John C, but if a (marine) engineer doesn't know that, run a mile!

[Sula]

Aug 19, 2020 7:17:03 GMT Sula said:

*I seem to remember someone had a problem with a Bukh 20 which turned out to simply be the rocker cover had been tightened down too hard, which compressed the rocker cover gasket, and resulted in something (decompressor?) holding the valves slightly open. In the course of investigating the problem he found that not all the gasket on sale were the same thickness. I can't remeber the exact details but will try to find the thread later in case it is of any help to you.

I've now managed to find the relevant thread, but I'd misremembered it, so it won't be any direct help to you.  The cause of the problem had been the rocker cover tightened down too hard and compressing the gasket, but the result was that it prevented the decompressor from working, but didn't affect the normal operation of the valves.  (It was also a DV24, not DV20.)

So the cause of your problem remains a mystery.

[jandane]

Alexander. The DV24 is the same engine as the 20 but with a different top and cleaner burning. I think the lack of approval in lake Constance is only a matter of administration, as it truly is a better engine. Is it not possible to change the approval with the local outhorities?
A total rebuild of a DV20 can be done for around 5500€ in Denmark.

[dolac]

Aug 20, 2020 9:49:54 GMT johnc said:

Aug 18, 2020 16:32:36 GMT alexander said:

Thanks Sula and Johnc for your thoughts!

I tried already to contact (through their website) Marine Enterprises during the last couple of days but they didn't reply until now. I think I will have to call!

I also learned in the meantime that the DV24 unfortunately isn't licensed for the lake of Constance where my boat is running, so it seems I will have to look for an older DV20 then.

And yes, that's what everybody told me until now, an old BUKH DV20 cannot be unrepairable... but my mechanic thinks there must be a hidden crack somewhere in the motor block because we don't have compression so we cannot start the engine anymore, and he tried out to repair and adjust anything else before to get it started again - without success. Also it seems that some water has got into the cylinders because there was some rust found within, therefore the idea of a crack somewhere in the motor block although we didn't see where it is.

I will let you know if I know more.
Alexander



The issue with water in the engine may not be due to a crack but may be coming back down the exhaust as the engine will be drawing lake water into the engine all the time the mechanic is trying to start the engine.   It is usually advised to close the seacock while trying to start a  difficult engine and open it as soon as the engine starts.

Did your mechanic open the engine? where exactly did he find rust?

When my dad bought our boat there were no internet and we didn't know DV20 common problems so we (he) had to pay our experience.. as we all know now, DV20 likes to overheat if there is no regular maintenance and our DV20 went into red and engine head got cracked.. that was 20+ years ago and since then (probably no one would believe me) but we didn't have any single problem.. even now, this year since march till august no one haven't been on the boat and when I arrived it started from the very first time (as always)..

so, if your mechanic didn't get engine head out, do it, check it, check valves and piston rings if there is no compression.. me personally, would not get rid of DV20

and another thing, if you didn't, try to get another mechanic opinion

we didn't pay much to weld the engine head, and it is much stronger now than originally, so think twice before you decide to get rid of DV20

keep us updated

[alexander]

Thanks everybody for their thoughts and contributions - very helpful, indeed!

Yesterday I went together with my old father (who owned the LM for 40 years before I inherited it, himself being a mechanical engineer) to see my mechanic and to talk once more how to go on with our Bukh DV 20. Unfortunately my father's experience was not of great help in the discussion...

The mechanic has opened first the cylinder head and now the whole engine more than once, checking cylinder head gasket, valves, piston rings and so on. He had built it together again twice without solving the problem of not-starting, with new cylinder head gasket, new valves, and still there was no compression. It's clear that the piston rings are not o.k. either, but he says that this is not the main problem. Nor is it the Dynastarter which has also a problem, but he says that's not the main problem as well.

Compression: he measured on one cylinder zero bar, on the second cylinder around 8 bar - instead of 20 or more bar pressure how it should be to get it started. And when reopening again the cylinder head he found again rust on the upper surface of the 2 pistons although had cleaned everything well before putting the engine together. So therefore his conclusion is that there must be a hidden crack in the motor block so that water from the cooling system can come into the engine and that would be the reason of getting no compression. But we don't see this crack of course which he says must be hidden somewhere inside the motorblock so we would not even know WHERE to weld it! And he says that in his opinion welding would not be a safe solution at all on the long run, so he still urges us to look for buying a new (means: used) DV 20 somewhere!

My mechanic is an old, very experienced mechanic who has done all his life a lot on old engines (on both oldtimer cars and ships) so it's for sure not that he's a beginner or nobody - but still... as long as I don't see the crack he's suspecting I just don't know what to believe.

So that's the situation at he moment.

to johnc: I don't understand how seawater could enter from backwards from the exhaust into the engine - between the engine and the exhaust there is no seacock! the only seacock is where the cooling water enters in front of the engine not after, so what would be the sense of closing this one?

[dolac]

after saying all these, guess your mechanic put a lot of effort to help you.... I said my engine head was welded and after 20+ years no problem, not even after cruising for 10+ hours ..

I would go for another opinion as it is "the cheapest" way before you make your decision.. really feel bad about your situation..

[chrismunson]

Sorry the engine is so ill! If the engine was cranked without firing for any length of time, there is no exhaust pressure to blow the cooling water out the elbow. Thus, the water backs up and eventually flows into the exhaust manifold, and the cylinders. Ruination prevails! (This is why never crank an engine for long without shutting the raw water seacock, unless you have fresh water with a heat exchanger. ) Since engine is so old, and has been thoroughly dissected and the problem not found, sadly and expensively its time to move on to a completely new or rebuilt engine. It really sounds like there is a hidden crack in the block.

[alexander]

Aug 22, 2020 7:36:10 GMT jandane said:

Alexander. The DV24 is the same engine as the 20 but with a different top and cleaner burning. I think the lack of approval in lake Constance is only a matter of administration, as it truly is a better engine. Is it not possible to change the approval with the local outhorities?
A total rebuild of a DV20 can be done for around 5500€ in Denmark.

Hallo jandane,
where in Denmark is such a rebuild done?
Second: do you know of any dealer or company in Denmark (or Scandinavia in general) that could maybe sell used BUKH engines (DV20 or DV24)?
Alexander