Bukh 20- cost-effective refurb?

[RobBrown]

My boat wil be out on the hard for longer than usual 4 weeks this winter, so some opportunity for working on the engine. This is a 28 yo Bukh DV 20. She starts OK ish (can be a bit stubborn when cold even with the air intake preheat). Once running, is absolutley fine, but recently getting some black smoke on start up only, but also if run at full revs ( c.3-3.1 K). Fine in between, but is obviously starting to use a fair bit of oil on running ( topping up a pint or so 4 or 5 times a season), so I am assuming problem is likely to be with cylinders, pistons & rings. Spent a fair bit a couple of years ago on a professional head & valves recon ( as could leave engine in situ). All other elements/peripherals & ancillaries seem fine.

Any thoughts on what further work could/should I think about getting done to try & resolve this problem cost effectively and generally keeping the old gal up to snuff? i.e. without getting any where near to the level of total costs where a replacement recon unit looks competitive (seen some on Boats & Outboards for around £2.5K). Not able to do complex engine work myself, tho I can pass over a spanner!

Rob

 

[cliff]

Replace the cylinder liners and fit a new set of rings but keeping the old pistons if possible. - there you go - an engine ready for the next 28~30 years

 

[AntarcticPilot]

Get the injectors checked and refurbished. Black smoke sounds like injector trouble. Not expensive to do, but it's a professional job.

 

[greenalien]

When you had the head off last time, did you check the bores for wear? That will inform you as to whether you need new liners (around £200 each), or can just get away with new piston rings (around £70 a full set). In either case, looks as though you'll need to pull the engine out, in which case plan on replacing the flexible mountings as well (around £200). Good advice about the injectors, easy to get refurbished at your local diesel fuel injection specialist, should leave you change out of £100.
If you're going to take the engine out, it's probably also worth getting the main fuel distribution pump checked as well; and the block will probably want a repaint.

 

[VicMallows]

I would recommend also renewing the gearbox input and output oil seals if you have the engine out. On my Sadler29 the output seal can be done in situ, but removing the gearbox to get at the input seal is impossible without releasing the engine from its mounts and jacking up the rear. (My BUKH20 is 26yrs old and has never needed attention other than gearbox seals).

Vic

 

[RobBrown]

Thanks for the replies gents. The injectors were looked at by the marine engineers (Bukh specialists) at the same time as the head was done and were pronounced fine at that time, which was about 18 months ago. I sort of assumed the black smoke equated with the burning of oil- no evidence of any sigificant loss of oil through leaks. She runs absolutely fine after start up, except at absolute full throttle when she still runs without mising a beat, but I get the black smoke. ( I was attempting what I believe is termed an "Italian tune -up"!). No specific comments on state of cylinders in course of last major work, tho general comment that a proper recon would usually involve the bottom end too. I couldn't afford it, so opted for the head work as the engineer's recommened best bang for my available buck at the time, around £1K then.

I thought piston rings would be an absolute minimum, but I guess if we're looking at liners as well then on GA's figures, thats £500 minimum straight away, plus labour & costs of getting the engine out and back in. Any idea of rough labour times, so I can get a ball park total figure? If I could achieve it for around the grand mark, especialy doing the suggested seal replacements @ same time then possibly a goer. I guess I could at least do any engine repaint and cleaning of the engine bay myself!


Sources of Bukh spares I know of are T Norris & French Marine as well as the (very helpful) guys @ Poole themselves, but prices unsurprisingly v. similar and a lot! Anyone know of less expensive ( if not cheap!) sources or alternatives? I did recall a recentish thread re alternative engine mounts for the Bukh 20 which were about 1/2 the cost, but can't recall the supplier nor relocate the thread.

 

[TQA]

If it ain't broke, don't fix it!

It does not sound broke to me.

If it starts easily, OK I hear what you say about cold weather starts, and runs at normal rpm without excessive oil consumption then I would say leave well alone.

BTW If you must go down the route of new liners/rings change all the crankshaft bearings and big end bearings too.

 

[RobBrown]

@TQA

But it is now using a lot of oil, and producing black smoke @ start up & at high revs, which it didn't used to, so something is gradually happening! I assure you I am not anxious to spend the money, but I would rather keep the exisiting engine going & reliable than simply carry on regardless, if that leads to a more expensive or even terminal result!!

I hear what you (& others) say re bearings etc- Problem is with also doing other work @ the same time is -is it really required, where do you stop & ending up with situation outlined in my opening post- work ending up costing more than a recon replacement or even worse , half way to cost of new engine and still having a 28 yo engine to show for it!! It's why I am trying to get opinions on what max benefit for min spend!

 

[charles_reed]

It's a finely balanced equation. Rebuilding the whole engine will not be an economic proposition, far cheaper to re-engine.
However where do you stop, once you have gone to the trouble and expense of taking the engine out?
Because you've had a head overhaul, the black smoke may be due to unburnt fuel when you open the governor up (unlike ic engines diesels rely on more fuel alone rather than total charge to speed up).
So, on the limited information you've supplied, I'd cast my vote with the leave-well-alone brigade.
A really experienced Bukh engineer, on site, testing the engine will give you more valid information than any of the well-meaning, but starved-of-information forumites - so before doing ANYTHING I'd suggest getting one of those aboard to advise you.

 

[PeterGibbs]

If it ain't broke, don't fix it!

It does not sound broke to me.

If it starts easily, OK I hear what you say about cold weather starts, and runs at normal rpm without excessive oil consumption then I would say leave well alone.

BTW If you must go down the route of new liners/rings change all the crankshaft bearings and big end bearings too.

Oh, the wisdom drips from this response:

How many engines smoke when on full heat - yup, loads. Need to rebuild, jank out the injectors - no. What happens when you leave it on full power to get to operating temperature - aha, the smoke subsides. and the prop keeps on turning.
But it's worth while checking the valve clearances - easy job with the cap off.

Bukh's are noted slow starters - squirt a drop of oil in the air intake and hey presto. Or use some Sure Start which the Bukh is well able to handle - unlike some other diesels.

Regular oil use, we note - no probs there: leave cyclinder liners alone etc etc

Hey fellah, you got a reliable engine. Potential probs?

Two things worth keeping a watch on - the raw water pump seals go quite regularly, and the circlip on the pump drive shaft has to be in place to shed water migrating inwards towards the engine. Want something to do to show your engine you love it? Replace the seals on that shaft - easy DIY.

And, the engine mounts will eventually go spongy and put the engine out of true alignment - get onto that sooner rather than later.

Bukh's go forever...but they don't need more than basic care.

PWG
(9 seasons with the Bukh 20.)

 

[RobBrown]

Thanks for everybody's input, but have to say after all the genuinely helpful comments, more confused than ever! I read straight across that high oil use (and it is now high- got through most the best part of 4 litres over this last season- after the oil change!) was a bad thing, that the black smoke at start (or very hi revs even after engine was well warm) was as a result of the burning of engine oil that got into the combustion chamber & that would be sensible to do something about it, but now I'm not so sure. I always intended get some professional advice based on an actual exam of engine but wanted to be up to speed with likely issues and costs to try & ensure I wasn't being pulled or pushed into directions & expenses which weren't really necessary, given my lack of technical knowledge. Message is perhaps I need to trust professional advice, but I feel I have been let down on that score before

Cheers chaps

 

[30boat]

IMHO a Bukh doesn't go forever and I've replaced two that didn't.After a certain point they become uneconomical to repair and you'll never relax not knowing whtat's going to go next.If your rings are worn and your oil consumption idicates that they are,you'll need a rebore and pistons or a rebore or new liners and pistons.You can get away with a hone and new rings but that may not last long.By this time your valve seats may need a regrind if you're lucky or new seats and guides (and valves) if you're not.The main bearings and big ends are likely to be ok if the oil has been changed often enough.These engines usually die by the cooling system wich gets clogged with salts.The waterways can be cleaned but in the end you'll always have an old engine.These are long lived if antiquated engines but they're not eternal.

 

[RobBrown]

Not Eternal

Yes I sort of know that intellectually, but whilst she is still generally performing OK, if a grand now gave me 4-5 seasons of relatively trouble free usage, it would look a reasonable trade off to me, particularly if a recon replacement at £2.5-3K would pot. offer little more in the relative reliability stakes. As mentioned, the injectors, head and valves were done professionally within the last 2 years, together withh the raw water pump & hoses. I do at least know first hand the last 6+ year history of this engine and its overall current state and a brand new replacement engine is entirely out of the question.

As a general addendum to previous posts, I have found the supplier mentioned in an earlier engine mount thread and supply the link for any Bukh 20 owner coming across this thread later:

http://www.avindustrialproducts.co.uk/products.htm

Don't know the costs or quality, but recall they were suggested as a source of spp alternative mounts for the Bukh 20. 4 Bukh mounts £205 from T Norris.

 

[RivalRedwing]

I wouldn't worry too much about using some oil, you used 4L over a season (how many hours?), I used to run an old Hillman Imp that shifted about a pint of oil per 2 hours of running but the engine ran very reliably - you just had to remember to do regular top-ups. If it is simply burning it via a bit of piston blow-back then it is unlikely to suddenly get worse and topping up the oil is by far your chepest option (?£15 per year). As others have said, partial refurbs could well call for further work after a couple of years - save your pennies for a new engine and in the mean time give the current engine some tlc and keep the oil topped up.

 

[RobBrown]

I'd guess 80 or so hours this season, tho oil consumption has definitely increased over the course of it. Rate of usage recently looks similar to your Imp! Motor-sailed c. 2 1/2 hrs from Hamble to Shalfleet against the tide on Sat am, doing around 2200 revs and oil level fell from mid way hi-lo marks on dipstick to under the low shoulder marks and was prob about 1/2-1 litre to top back up.

I will have a word with a marine engineer I know whose judgement I do trust & see what he says, but maybe laissez-faire will prove the best option in the end.

 

[SAMYL]

You can buy an awfull lot of oil for the cost of an engine refurb and as others have said 'if it aint broke don't fix it'.

Holts used to market an additive called Piston Seal which worked very well for me on a couple of occasions with oil loss due to piston blow by. Once cutting a quart per 100 miles in an old Austin van down to virtually nothing!

Not sure if it is still available but another manufacturer does make something similar and I have heard good reports about it recently. Worth a try, sorry I don't know the name.

 

[RobBrown]

Update

Thought I'd psot an update that might be of interest/help to fellow DV20 owners. I rank Bukh @ Poole & spoke to Al Pearson, who as always, was extraordinarily helpful. In his opinion the black smoke was unburnt fuel, not linked with the oil loss, on basis burnt oil was usually blue-black and times when it was released- on start up (when system initiallydelivers more diesel than will be consumed) and high revs under load - poss down to fouling as I am not underpropped..

However, the rate of oil loss was likely to involve piston by-pass if no evidence of any signifcant oil leaks and then yes, new rings could be considered, but in his opinion, rare to require new liners and if no evidence of any bearing problems, or gearbox seals going, no need to change those simply because engine might be coming out, tho might consider the input seal because of access and lowish cost of part. Surprising element of cost is the main gasket set, which is around £138 plus VAT!

However if liners are not required, then overall cost with labour should hopefully be within my budget. Any higher & it would be marginal. Al confirmed that fully recon units were going for around £2500. Or he could sell me a new 24 for £7K (whether inc or excl VAT, I didn't ask)!

Anyway after discussing with him, I will ask a good guy I know to take an initial look, see if that level/cost of refurb looks on & then have a further word with Norman @ Bukh before embarking on anything, @ Al's suggestion!

Also, for info in my searches, found an outlet with occasional new & used Bukh spares at reasonable prices:

http://www.boatpartsandspares.co.uk/