Bukh DV 20

[Tranona]

You'll need to explain that to me in wee words .
My shaft anode appears to have looked after my prop perfectly well.
The engine is wired to the hull anode and appears to have suffered no ill effects in the several decades I've owned it.
Given that it's raw water cooled, then isn't it effectively in the required electrolyte?
I was told many years ago by a naval architect that anodising a vessel was a black art .

I have already explained it. The anode needs to be in the same water (electrolyte) as the bits it is protecting. The anode in your engine cooling system is there to protect metals in the cooling system that have different potentials. Zinc has low potential so erodes rather than the other metal. Your hull anode is NOT in the same water as the cooling water in the engine.

This explains how galvanic cells work en.wikipedia.org/wiki/Galvanic_cell and this explains how sacrificial anodes are used to prevent corrosion mgduff.co.uk/knowledge-base/cathodic-protection

With regards to your engine the makers clearly believe that there are metals in the raw water cooling circuit of different potential that represent a potential corrosion problem from galvanic action and that a sacrificial anode will reduce or prevent this. If this were not the case why would they bother. Many engines do not have internal anodes - all small modern Volvos for example because their heat exchangers do not have metals of different potential in the seawater side.

The hull anode may be connected to the engine, but that is normally to make a circuit to the shaft and propeller. The anode is in the circuit to stop dezincification of the propeller. To be effective it has to be electrically connected to the shaft and position close by in line of sight with the propeller. Alternatively if there is exposed shaft, for example if a P bracket is used to support the shaft, a shaft anode can be used instead as in your case. this suggests your hull anode serves no purpose and could be removed. It is definitely not a substitute for the engine anode.

There is no "black art" about using anodes, but a high level of misunderstanding or even ignorance among many including regrettably some surveyors. The principles are very simple - dissimilar metals in electrical contact in water, which is an electrolyte, particularly seawater. On a typical small sailing boat the main items that need protection are propellers, saildrive housings, bow thrusters and in some cases rudder stocks and fittings. As already suggested engines vary, but if an anode is needed the maker will fit one.

My boat is just about as complicated as you can get for a shaft drive sailing boat. The Beta engine has an anode in the heat exchanger. The shaft is stainless and the feathering propeller is a mixture of yellow metal (bronze) and stainless. The propeller has its own anode, but its size is limited so a hull anode is fitted as a backup. It is not connected to the engine because there is a flexible coupling so the circuit to the propeller is made through a contact running on the shaft. The photos show how it works. The first is the hull anode close to the propeller, second is the propeller with the anode on the end of the hub and the third is the connection to the shaft.

 

[vyv_cox]

You'll need to explain that to me in wee words .
My shaft anode appears to have looked after my prop perfectly well.
The engine is wired to the hull anode and appears to have suffered no ill effects in the several decades I've owned it.
Given that it's raw water cooled, then isn't it effectively in the required electrolyte?
I was told many years ago by a naval architect that anodising a vessel was a black art .

A shaft anode is in close proximity to the galvanic couple of propeller and shaft. It 'sees' the propeller, thus the combination is close to perfect.

With a hull anode you are asking the ions to pass around the hull, make a right angle turn into the skin fitting, run through a hose as if it was a length of wire, somehow get past the vanes in the pump and eventually reach the engine. Sorry, it just is not going to happen. Under normal circumstances ions like to move in straight lines, not very far. For example, on subsea pipelines anodes are placed every five diameters.

Most raw water cooled engines last well even if the pencil anode is not replaced regularly. They are very small for the amount of ferrous metal they are asked to protect and they will never 'see' the whole engine. Despite this severe corrosion is rare.

 

[Neeves]

I thought these small Bukh engines had a decompression lever (and a hefty flywheel) allowing hand starting - or was that limited to the DV 10. The DV 10 was very, very simple. Hand starting the DV 10 was an art and required all obstructions, saloon table and crew, to stand well back.

The company has not been running without issues - they had major financial problems, early 1980s (so a long, long time ago) forcing X Yachts has to discontinue use in the X-99, replaced by, I think, a 10hp Volvo. Bukh must have been rescued. Their major market was lifeboats.

Jonathan

 

[vyv_cox]

I thought these small Bukh engines had a decompression lever (and a hefty flywheel) allowing hand starting - or was that limited to the DV 10. The DV 10 was very, very simple. Hand starting the DV 10 was an art and required all obstructions, saloon table and crew, to stand well back.

The company has not been running without issues - they had major financial problems, early 1980s (so a long, long time ago) forcing X Yachts has to discontinue use in the X-99, replaced by, I think, a 10hp Volvo. Bukh must have been rescued. Their major market was lifeboats.

Jonathan

My DV20 was theoretically capable of hand starting but the handle needed an additional support, similar to the hole in the front bumper on old cars. There was no such support on mine so it was a non-starter

 

[Neeves]

My DV20 was theoretically capable of hand starting but the handle needed an additional support, similar to the hole in the front bumper on old cars. There was no such support on mine so it was a non-starter

The DV10 had a big horizontal flywheel on top of the engine. You removed the engine cover and took a supplied bit of rope, it had a knot at the end. You secured the knot in a slot in the top of the flywheel and wrapped the rest of the rope round a notch round the circumference of the fly wheel. You made sure you would not hit the saloon table, nor crew, and put as much griunt into pulling the rope and hey presto the engine would start. I cannot recall how the decompression lever 'locked op'.

Flywheel was part of the alternator, all the cabling and wires were in the underside of the flywheel, and we had a 60amp car battery to run the electrics.

Simple stuff - provided you had 'grunt'

Jonathan

 

[chriscallender]

I thought these small Bukh engines had a decompression lever (and a hefty flywheel) allowing hand starting - or was that limited to the DV 10. The DV 10 was very, very simple. Hand starting the DV 10 was an art and required all obstructions, saloon table and crew, to stand well back.

The company has not been running without issues - they had major financial problems, early 1980s (so a long, long time ago) forcing X Yachts has to discontinue use in the X-99, replaced by, I think, a 10hp Volvo. Bukh must have been rescued. Their major market was lifeboats.

Jonathan

The DV20 has decompression levers as well. Hand starting was (at least) an art, I never managed it from cold despite trying. If the engine was already hot or at least a bit warm it was doable, it caught pretty easily. I Perhaps I needed to tame a friendly gorilla as crew for the cold starts.

 

[LittleSister]

I thought these small Bukh engines had a decompression lever (and a hefty flywheel) allowing hand starting - or was that limited to the DV 10. The DV 10 was very, very simple. Hand starting the DV 10 was an art and required all obstructions, saloon table and crew, to stand well back.

The DV10 had a big horizontal flywheel on top of the engine. You removed the engine cover and took a supplied bit of rope, it had a knot at the end. You secured the knot in a slot in the top of the flywheel and wrapped the rest of the rope round a notch round the circumference of the fly wheel. You made sure you would not hit the saloon table, nor crew, and put as much griunt into pulling the rope and hey presto the engine would start. I cannot recall how the decompression lever 'locked op'.

Flywheel was part of the alternator, all the cabling and wires were in the underside of the flywheel, and we had a 60amp car battery to run the electrics.

Simple stuff - provided you had 'grunt'

Jonathan

Jonathan, I think you have perhaps confused the Bukh DV10 with some other engine (sounds like an old Seagull outboard!). The DV10 flywheel is (like all the DV series) on the front of the engine, not on the top of it. It is not at all part of the alternator (which is a standard separate automotive type alternator driven by a belt). Neither my DV10 nor my DV36 had any wiring under the flywheel.

It is precisely the fact that the Bukh DV series has a practical hand-start facility that is why it is still manufactured today - as this is apparently a requirement for lifeboat engines, which is the bulk of the DV series new sales these days. (Bukh today also produce a lot of other, much bigger and more sophisticated engine series.)

I previously had a DV10 (which always started easily, by the way), and starting it was not all the major operation you describe. I simply removed the front cover (integral with the companionway steps on my boat) and inserted the crank handle in the socket on the front of the engine. The decompressor lever is on top of the engine, accessible from the front, as shown in the following pic from the DV10 Owner's Manual. [EDIT - It would normally be started by the battery, of course, I only started it by hand to prove to myself it could be done if need be.]


You do not use a rope to start a DV10. There is no facility to attach such a rope. The starting handle is a hefty metal traditional type crank-handle (with a cylindrical rotating sleeve on the hand grip). The drive socket for the starting handle is on the front of the engine on the D10 and 20. In all the DV series the handle does not go direct onto the flywheel, but into a dedicated socket which connects to the crankshaft (or is it the camshaft? I forget now) via a chain.

On my DV36 (and presumably the DV24) the socket is at the rear of the engine and above it, so can be started either from behind the engine (installation permitting) or, with a longer starting handle, in front of it. On the front of the engine is a bracket with a guide for the long starting handle - presumably it is that bracket that Vyv had missing from his engine (see post #24).

The company has not been running without issues - they had major financial problems, early 1980s (so a long, long time ago) forcing X Yachts has to discontinue use in the X-99, replaced by, I think, a 10hp Volvo. Bukh must have been rescued. Their major market was lifeboats.

Bukh was a very long established Danish company, producing tractors (and I don't know what else). Yes, they did have financial problems in the 80s, but I think that was eventually resolved by some sort of management buyout.

During that period of financial instability and before it was resolved, output was somewhat intermittent and yacht builders who had previously fitted Bukhs switched to other brands. When full output was restored some reverted to Bukhs, and presumably others continued with their new suppliers.

Today DV lifeboat engines are just a small part of their business, which includes marine engines up to 700hp.
Velkommen til BUKH A/S

 

[Misterbreeze]

I hand started my DV24 once, purely to see if it could be done. At 70 I'm no Charles Atlas (and never was) but still managed. Don't underestimate the effort needed to spin it fast enough though! The tricky bit is doing it one-handed whilst holding the decompression lever open with the other one. It would be much easier with an assistant, if they can reach without getting their arm broken.

 

[alan_d]

I quite understand and you haven't quite read my post.

Please explain what you think I have not read.

 

[LittleSister]

My 1983 DV36 has been reliable for 15 years. . . . I’m at loss and unless a cause can be found I’ll be forced to re-power, which will be such a shame, I love this engine, but can it be saved?

This poster wrote this appreciation of his/her Bukh on another current thread, despite having a serious and mystifying fault at the moment.

Bukh dv36 raw water pump shaft

 

[Neeves]

For the DV10 and 20 this has some useful links

Bukh DV20 and DV10 diesel engines - Cruisers & Sailing Forums

Jonathan, I think you have perhaps confused the Bukh DV10 with some other engine (sounds like an old Seagull outboard!). The DV10 flywheel is (like all the DV series) on the front of the engine, not on the top of it. It is not at all part of the alternator (which is a standard separate automotive type alternator driven by a belt). Neither my DV10 nor my DV36 had any wiring under the flywheel.

It may be that my memories are jaded - but I could not fabricate so much, I lack that level of imagination

I wonder if X-yachts had the DV 10 modified specifically for the X-99 and for the sail drive. The DV 10 came in at least 3 versions.

I confess that pictures of yacht engines was not my forte then, nor really - not now either, - So I don't have any pictures

But on the assumption I'm wrong - the link will be useful - and the Forum, as usual, excels - and auto, well almost auto, corrects

Jonathan