Air cooled inboard ??

[Madhatter]

With all its inherent problems ( holes in hull,corrosion,pumps, etc) the diesel water cooled engine seems to be to be a calculated risk, so I wonder why more aircooled engines are not used ?
I am sure there must be a reason but I can't see any that can't be easily overcome , But I would love to hear any advice about the pro's and cons of this.

 

[haydude]

With all its inherent problems ( holes in hull,corrosion,pumps, etc) the diesel water cooled engine seems to be to be a calculated risk, so I wonder why more aircooled engines are not used ?
I am sure there must be a reason but I can't see any that can't be easily overcome , But I would love to hear any advice about the pro's and cons of this.

I wondered the same thing, given that one may divert the air flow to heat the inside during the winter.

I believe the answer is that it would require a large radiator and a fan always running which would give some challenge in where to place it. The fan in particular would take away considerable electric power because you cannot rely on the air been forced at speed through the nose like with cars.

 

[Bosun Higgs]

noise. big time. and how do you get rid of the heat but via holes in the deck?

watercooled engines arent a problem really. neither are holes in the hull.

 

[NickRobinson]

Listers (aircooled) were common on canal boats, especially hire boats as 'fool proof'. ie no temp alarms/inlet valves to ignore

Main prob seems to be that they are noisy ( unlike my Yanmar single pot YSM)

Nick

no elec fan needed, fins cast onto flywheel is usual

 

[aluijten]

Noise is big part of the problem but only because the volume of air required to cool the engine is huge compared to water. To increase 1 dm3 (= 1 liter) of water by 10 degrees you need much, much more energy then for 1 liter of air.
So the heat drain for air from the motors point of view is much less per quantity of cooling medium when you compare water with air.
Because of this you need a huge flow of air through the radiator => noise.

 

[Madhatter]

Thanks for all the replies.
The way I am reading it so far is
against
1/ noise
2/electric usage ??maybe dependant on engine
3/moving sufficient air to cool

for
1/cheaper engine
2/lighter engine
3/ less corrosion

 

[prv]

You'd need a lot of airflow, which is problematic for something that might be used in rough water. I think some inland boats have used them, as they can have big holes in the side of the boat without too much difficulty.

What you *can* do is have a water-cooled engine but with a closed water circuit. Then you presumably fill it with chemical coolant diluted with clean water (like a car) and suffer no corrosion problems. If the system does leak, you're only going to have to mop a few litres out of the bilge, not recover the boat from the bottom of the harbour. Obviously you need a heat exchanger of some kind - ideally you have a steel hull and can just weld a long thin box onto the inside of it, through which you pass the coolant to give up its heat. Or I have seen a couple of wooden hulls with metal pipes running along the outside of the garboards (probably a little more vulnerable to damage).

Google "keel cooler".

Pete

 

[[448]]

Many years ago I had a boat with a Lister 3 cylinder 13 hp engine. SL3 was the model and 1948 was the nyear built. These were proper horses and the boat, a heavy teak motor 33 ft motor sailor never seemed under powered. The cooling fan was built in - therefore no electrickery. The cooling air was ducted to a port located in the cockpit - therefore no intusion. This could be diverted to the cabin in cold weather, and yes the cooling air was fresh.
The noise by today's standards was excessive, but you got used to it.
That engine never failed to start, never stopped involuntarily and used a thimble full of diesel in a day.
I don't think it would be impossible to produce a modern air cooled diesel which ran at a reasonable noise level.
And yes, the absence of cooling water was a bonus.
Dave

 

[JimC]

They are terribly noisy though, think of the air-cooled diesels used in dumper trucks etc. I guess it would be difficult to insulate the noise whilst still allowing passage for the cooling air.

 

[DownWest]

You also need to run a hot exaust, OK on a fishing boat where it goes straight up, not so easy on a yacht with lagged pipes running aft and heavy silencers.
I had a bit to do with aircooled Listers in gensets. It is possible to quieten them down, but needs some space and again, lots of air with baffled ducting. Not to forget, gearboxes are often watercooled as well.
Just to give you an idea, the outlet duct for a 35kva Lister genset (engine only) is around 700x250mm.
I was asked to install such a unit in an up-market villa as stand-by. Just the money I spent on keeping it down to a murmour would have re-engined a 30ft yacht.

 

[sarabande]

a fair number of farms still use air-cooled Listers in various configurations. They are not the smoothest of machines, and require gert big flywheels to smooth out the firing cycle.

You would need to have an air-powered heat exchanger to use the heat from the engine because of the risk of fumes. Given that, if you were careful with the air path, you could direct it astern and give yourself a couple of extra knots. Or mount one of those deliciously old-fashioned steamer air-intakes on the foredeck, and make it steerable, rather like a Harrier outlet.

Air-assisted mooring !


Other advantages - lots of dry air to warm up your soaking gear.

 

[Tranona]

Add to the noise and cooling problems the sheer physical space they take up. we used to have Lister 2 cylinders in our club launches. 12hp but about 3 times the size of a modern fresh water cooled diesel. Did keep you hands warm when doing winter Sunday rescue boat duty!

One or two peole have tried fitting marinised industrial engines such as JLOs into boats, but end up being more complicated by the time you build ducting for fan and figure out a way of cooling the exhaust - plus of course linking up to a gearbox.

 

[Latestarter1]

Listers, Deutz and a few others to boot.

Some Scottish built MFV's had Listers with Jabsco raw water pump for a raw water curcuit to cool the gearbox and exit via injection bend to cool exhaust. And do not forget ships lifeboats.

Apart from noise the sheer volume of air trunking eats up masses internal hull volume.

Anyway you cannot turn the clock back, air cooled diesel engines died because they became impossible to certify to exhaust emissions. Air cooled industrial engines are pretty much dead.

OP's original premise is a little flawed anyway, no problems with indirect water cooled small diesel engines, nine times out of ten down to the numskulls who install them incorrectly.

 

[cowpat]

Main Eng' NO : Gen' YES.

I think you can conclude that indirect water cooling is a better option...BUT not mentioned yet is the lovely secure feeling one gets when a Lister is tonking away providing reliable electricity. My Y.O.M. 1971 Lister LR1 has just had a bit of a topend overhaul. Parts available and easy to work on. I would not part with it any more than I would part with the Missis Y.O.M. 1969.

 

[Madhatter]

Thanks again for all the replies.
I have taken on board all the points made here and am left thinking that a hybrid system is the way to go,there are too many factors to explain here at the moment but the cost of fitting a marine inboard is huge ( in relation to the boat value)where as a small aircooled modern engine is 2K cheaper than its marine equivalent and to be honest even though reliability may be questionable the ease of changing the engine outweighs that problem (after initial fitting of total system). One last point is that due to the weight of a marine engine I could actually carry a spare aircooled engine with out any extra weight almost achieving a throw away scenario ( incoming abuse from the greens ).

I will report back when I have put more thought into the details.

 

[LittleSister]

Noise is big part of the problem but only because the volume of air required to cool the engine is huge compared to water.

Not only that important reason. The water jackets on water cooled engines help deaden the mechanical noise of the engine (e.g. compare air and water cooled motorbike engines), and I would imagine the ducting for air-cooling, by contrast would make a pretty good resonator to amplify/distibute engine noise.

I've also read that water cooling, by virtue of allowing the operating temperature to be more tightly controlled (presumably this would apply only to marine engines designed for indirect water cooling), allows tighter tolerances. Presumably this might also potentially contribute to lower noise levels.

Documents show our boat was originally fitted with an air-cooled 7hp Ducati engine. We don't know anything about the intervening history, but presumably this wasn't a resounding (geddit?) success as less than twenty years later it was replaced by a water-cooled engine.

 

[Tranona]

Thanks again for all the replies.
I have taken on board all the points made here and am left thinking that a hybrid system is the way to go,there are too many factors to explain here at the moment but the cost of fitting a marine inboard is huge ( in relation to the boat value)where as a small aircooled modern engine is 2K cheaper than its marine equivalent and to be honest even though reliability may be questionable the ease of changing the engine outweighs that problem (after initial fitting of total system). One last point is that due to the weight of a marine engine I could actually carry a spare aircooled engine with out any extra weight almost achieving a throw away scenario ( incoming abuse from the greens ).

I will report back when I have put more thought into the details.

Do a search on back numbers of PBO and there was an article not too long ago of somebody replacing a BMW D7 with an aircooled engine, using the same transmission. Clever bit of work, but suspect it will put you off the whole idea. If aircooled engines had all the benefits (including cost) you seem to think, somebody would produce them commercially. They don't have any benefits - raher the opposite - so nobody does.