MD2003 convert to freshwater?

[chris-s]

Having a sailing boat which is powered by an outboard, I had always assumed that when it came to inboards, apart from Bukh engines, others like Volvo's, Beta etc were all freshwater cooled. Over the last few months as we have started to look for a different boat I see that I am wrong in my assumption and that there are quite a few raw-water cooled Volvo engined boats out there.

Other than age and the potential of salt (dirt?) clogged waterways, is there anything in particular that should be considered when thinking about buying a boat with one of these?

Is it worth/practical to convert one to freshwater?

Thanks

Chris

 

[LittleSister]

Direct seawater cooling was the norm until not that long ago, and generally found adequate. The main advantage of indirect cooling is that the engine can be run hotter, which is more efficient. At those higher temperature the salts in seawater would be precipitated out rapidly and soon clog the waterways. The main advantage of direct seawater cooling is simplicity and cost, the disadvantages a marginal increase fuel consumption, marginally higher emissions and the likely occasional need to flush the engine with e.g. Rydlyme.

I don't think there's anything in particular to look out for on a seawater cooled engine.

Bukhs have always been available in both direct (seawater) and indirect (freshwater) cooled versions. Bukh manuals state that if the engine does more than 500 hours per annum (which few leisure yachts do), it is worth having freshwater cooling (but they don't state the rationale for that figure). Older Bukhs, once fitted to yachts as original equipment were usually seawater cooled. These days, because of their high cost and weight they are mainly only fitted to lifeboats and usually are freshwater cooled, and it is these ones ex-lifeboat ones that are often now available second-hand.

It is possible to convert a seawater cooled engine to freshwater cooling, but how practicable and expensive that would be will depend on the particular engine. For most people the marginal advantage isn't worth the bother and cost. You would need a circulation pump, a heat exchanger (available off the shelf from e.g. Bowman), a different higher temperature thermostat, and changes to the plumbing arrangements (which might involve modifications to the thermostat housing).

 

[vyv_cox]

A kit is available to convert the 2003 to fresh water cooling but as might be expected, it costs a fortune. There are so many raw water cooled examples of these engines in service that one wonders why anyone would want to convert them.
When my son worked for Sunsail he regularly converted fresh water cooled versions to raw water cooled to improve their reliability. The O-ring sealed copper tubing is very sensitive and proved not to be punter-proof.

 

[jamie N]

My experience was with cooling passages pretty much choked with salt/mud/shite, which required an awful lot of work to clean out.
Not your MD2003, but I converted mine to freshwater cooling for about £100. It's simple, reliable, uncomplicated and allows for multiple redundancies. Having put hours on it, I'd not consider converting it back.
All of it was with 'off the shelf Amazon' items, and I reckon would be easily accomplished by most with 'a clue'.
However, I don't know your engine, and should stress that mine's 9-10hp, so of a much lower kW output.
As others have said, many many many engines are raw water cooled, with easily cared for known issues therein, but my Autistic nature 'encouraged' me to change it.

 

[scottie]

Unless you are desperate for hot water quickly I would suggest that this horse has definitely bolted
and that corrosion will be alive and kicking

 

[Tranona]

As suggested not worth converting. One of the reasons Volvo stopped making these engines was that small industrial engines like the Kubota, Mitsubishi and the Perkins they moved to were coming on the market . They were far superior to their own design and easy to add a heat exchanger for freshwater cooling. Their major competitor, Yanmar were also changing to fresh, although they persisted with simple seawater cooled for some time with some models.

Now of course they are over 35 years old and spares beyond maintenance items are becoming scarce and expensive, but provided you don't need major replacements, they last well. Always tricky deciding whether it is worth buying a boat with such an engine. A replacement is around £8-10k for a 30hp, a little less for 20 so better perhaps find a boat where the job has already been done as the premium assuming the rest of the boat is comparable is small. Of course things are never as simple as that as there are other major replacements on older boats that can hit the wallet just as hard.

 

[jamie N]

Unless you are desperate for hot water quickly I would suggest that this horse has definitely bolted
and that corrosion will be alive and kicking

Yup, but that was one of the curiousities of my own engine, that once I'd the shite away from the inside of the block, there was no apparent corrosion?
The anode was 90% wasted, at least, but had been doing its job I guess,
Like you, I was extremely surprised as it was counter intuitive.

 

[johnalison]

On my then Sadler 29 the 2002 blew its head gasket after about four years and the engine had to be replaced as a repair to the head would not have been economic. I was this able to make a direct comparison between the old salt-water engine and its fresh-water replacement. The new engine ran hotter, of course, and much more sweetly, though I was not able to make a useful comparison of the fuel consumption. In addition, laying up was easier, leaving me with a great preference for f/w, even though I did take full advantage of it at the time by adding hot water heating.