Bukh dv 20

M

malcolmpaxman

New Member
Joined
20 Jul 2006
Messages
7
Visit site
Its fast aproaching that time of year again and I am pondering the winterisation process again. Does any one know if just removing the thermostat will allow me to flush through with fresh water rather than all the messing around with hoses and recirculating the water until the stat opens. I normally repeat the process with a couple of bucket load of fresh water to try and remove as much salt as possible and then fill with anti freeze.
 
Probably worth removing the complete thermostat housing from time to time. It is held in by quite long thin bolts with Allen key heads. They have been known to sieze and also corrode away. I used to take it apart every 2-3 years, clean and use some Copper grease on bolts. It was a pain the first time I needed to remove it and needed new bolts. However, it never gave any trouble again.

Assuming you are flushing with fresh and finishing with antifreeze:
Each winter, I always removed the large plug under back of manifold, one on side of block underneath that and one at back with finger anode. You get a lot of rust out with the antifreeze so worth poking with a stick in the lower side hole as it drains.

PS
I used to do the oil change before lift out as it was easy to get the engine nice and warm on a short run. Then I'd get it warmed up prior to lift out and connect inlet to my shower outlet (big bucket would do as VicS suggests). The run over to the crane berth gave it plenty of time to flush and I could finish with dilute antifreeze then a pint of neat stuff.

I found that this was a pretty painless way of starting winterising. Antifreeze in the block could be drained at a later date with little effort.

Might be worth trying that next year.
 
Last edited:
Interesting to note everyone's different approach. My 1984 BUKH20 has never been 'winterised' in any way. Afloat all year, and sometimes not started for a couple of months over winter. No problems whatsoever. South (Chichester) may be relevant.
 
Bukh do recommend running with fresh water each year as part of the winterisation programme, but I'm not sure why you use antifreeze. Enough to drain the water, remove the impeller, and plug the exhaust and air inlet, i'd have thought.
 
cimo said:
Bukh do recommend running with fresh water each year as part of the winterisation programme, but I'm not sure why you use antifreeze. Enough to drain the water, remove the impeller, and plug the exhaust and air inlet, i'd have thought.
Click to expand...

That's what I always did with my Bukh. The only advantage I can see in adding antifreeze is that it contains a corrosion inhibitor. But the very small amount of fresh water that remains inside after a flush is not going to have a severe corroding effect on cast iron. Better to drain it and make sure the drain taps are not blocked with rust sludge, as mentioned above.
 
In my case, the drain tap on stainless muffler never worked so antifreeze in block & exhaust was belt & braces for the block and avoided an problem with the water trapped in the muffler.

Remember, this was in Scotland and -25C wasn't unheard of in winter. More usually -5 to -10 but still enough to cause problems. Pretty paranoid about flushing water tank, shower & pipes as well. Didn't have any problems in 23 years with that boat so seemed to work in very worst winters.
 
VicS said:
If you just flush and drain it will be left wet and full of air. This is the recipe for maximising the rusting that can take place. If it were not for the freezing risk full of fresh water would lead to less rusting as the amount of oxygen available will be less.

Adding antifreeze not only prevents freezing but the corrosion inhibitors it contains prevent rusting.
Click to expand...

Cast iron does not rust rapidly in damp air. Have a look at a few drain covers, manhole covers, etc, some of which have been exposed to British weather for more than 100 years. My toilet standpipe at home is cast iron, as are some of my gutters. Some of these are definitely 100 years old.

There are thousands of raw water cooled engines with lives of many decades that have never been winterised using antifreeze. Iron castings are always heavy to give adequate resistance to brittle fracture, which also gives them an enormous corrosion allowance.
 
VicS said:
So all the recommendations in engine manuals and elsewhere so winterize by filling with an antifreeze mixture are a load of nonsense.

Just flush and drain then?... That makes life a lot simpler!
Click to expand...

Both the Bukh and Yanmar workshop manuals state that their engines can either be drained or filled with antifreeze mixture. Nowhere does it give a preference. I have two scanned Nigel Calder articles on winterising and in each he gives the same advice. When I had my Bukh I only flushed it, although at ten years old I was probably the first owner to even do that. I partially stripped it at around 17 or 18 years old and found no noteworthy internal corrosion.

'Load of nonsense' are your words. I wouldn't go so far but I seriously doubt the necessity.
 
As a newcomer to boating I found these postings very reassuring. I have a Colvic 20 with a Bukh 20 in it. I towed the boat down here to Greece from the UK [NEVER buy an Indespension trailer guys - what a nightmare it was and the company have been real *******s] and the boat was craned in to the Med in October. The Bukh20 started first time. I only ran it for a couple of hours before the boat went into the local boatyard on this tiny Greek island. I've drained the block and replaced the pencil block anode. I also changed the impeller and smeared the new one with vasseline before fitting. I've hand cranked the engine a couple of times a month, just to keep it turning, though I don't expect with an average 10 degrees sunny weather in the winter to have any seizure problems. I did find the advice about the thermostat particularly helpful. I plan on taking the thermostat out because the average sea temp in the summer is about 23 degrees C and the ambient air temp in the daytimes is around 75-85 F. Apart from changing the oil as couple of times to get every drop of the old stuff out, have you guys any further suggestions? I do wonder if there's somewhere one can register an engine number. Hmmm? Thanks guys. This is a boon to a newcomer.
 
Don't take the thermostat out! In the first place the engine needs to get to working temeperature as quickly as possible to avoid excessive wear. More importantly, the thermostat in a raw-water cooled Bukh engine is not the same as the one in a car. It works as a diverter valve, directing bypass water around the engine or through it for cooling. If you take the thermostat out you run the risk that all the water will go via the bypass, so the engine will boil, or at least run too hot. The consequence of that is excessive carbonate deposits that will prove very difficult to remove.
 
+1!.
But I want to mention waterpump - take good look - older type was leaking water into engine if shaft or bearings got worn, and it could go unnoticed. Better to make a whole service of pump for peace of mind.
In case it's worn - I heard it's better to buy new kind of pump, improved.
 
Rossynant said:
+1!.
But I want to mention waterpump - take good look - older type was leaking water into engine if shaft or bearings got worn, and it could go unnoticed. Better to make a whole service of pump for peace of mind.
In case it's worn - I heard it's better to buy new kind of pump, improved.
Click to expand...

+2 for not removing the thermostat for reasons given by Vyv. See my earlier post regarding removal it to clean inside the housing to check it and replace if required.

The pump shaft should have cheap seals at either end, one for water and the other for oil. There should be holes in the outer tube behind the pump and they should be kept clear. I've seen them full of gunge and painted over on some DV20s. If a seal does leak you should see water or oil on the engine underneath the pump. It is also quite easy to pull the shaft out for inspection when replacing the impeller. So you can check whether it needs to be replaced.

Wear on the pump faces tends to be a bigger problem and this usually shows up as problems priming after sailing. Air gets into the inlet and the pump action isn't strong enough to pull water through. Watch out for that issue.
 
Last edited:
Wow. That's great advice. Thanks very much. I didn't know about the differwence in operation between a Bukh and a car. I think however I will try to gently take out the two long allan head bolts which hold the thermostat housing on and inspect the inside for operation and build-up. But I most certainly will not remove the thermostat. I see you're sailing in the Med. If you're ever passing Agistri island in the Saronic Gulf, I'd be happy to buy you a drink.
 
I'm happy to report that the thermostat in my Bukh 20 is now replaced! When I bought the boat in October the seller mentioned something to me about sailing in the warm Med and the thermostat, but with 1001 other things to remember I'd forgotten. The thermostat was aboard in a plastic box marked 'Thermostat' and the spring opened when pushed. The rubber surround was in good condition. All I had to do was loosen the two 1/2 inch head-size long housing bolts - which came easily as the seller had greased them when he took the thermostat out while the boat was moored in Wales. Then I scraped out the gunge that had built up in the groove where the thermostat rubber should have been, and refitted the thermostat. I re-greased the two bolts and made sure not to over-tighten them. Job done. Who said Bukh 20s were troublesome? Not me.
 
Hi Vyv, A piece of your excellent advice would be appreciated. The subject is re-sealing the water-cooled prop shaft seal after launch. I've just discovered that this is required and read this advice "The prop shaft seal, which is water cooled, must be vented after launching by compressing it at the lip of the seal at the same time as it is pressed toward the prop shaft. When water forces its way out of the gap the seal is vented." Can you add anything to that as 'compressing' and 'pressing' seem to me to be the same thing. Some practical words of wisdom would help. Many thanks.
 
I assume this is either a Volvo or something similar? You only need to press on opposite sides of the seal with thumb and finger until water runs out. This expels the air that will be trapped in the upper part of the seal. However, I am a little confused by your description of 'water cooled' which implies a vent tube, in which case air should not be trapped. Photos of most types are on my website, which will help you to identify what you have.
 
You must log in or register to reply here.

Other threads that may be of interest

geem
First 6 months with no gas onboard
2 3
Replies
41
Views
1K
Baggywrinkle
Baggywrinkle

Share this page

Top