seems to say you can't use air-cooled diesel in a boat

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Why couldn't you just duct the heat out of the engine compartment?

My experience with air-cooled diesel generators at construction sites was that they were the loudest thing ever, so I guess that would be plenty of reason not to use air-cooled diesel on a boat.

Except for those nasty diesel generators, I don't recall any civilian air-cooled diesels.

 

I’ve run lots of those Deutz air cooled generators and air compressors on job sites, and they are definitely loud!
I could often still hear them when home in bed.
Hot air is also a huge byproduct of their operation, a large stack would be needed to get that heat safely away from the boat.
The price is attractive.
They’re covered with sheet metal shrouding and cooling fins, I doubt they’d survive well in a salty atmosphere.

 

Plenty of boats used to have air cooled diesels, even relatively big ones. Drawbacks are space for the air ducting and noise. They can also use a wet exhaust, but the advantages over water cooling disappear.

Kohler sells a marine generator with a hybrid air/water cooling called the LMG 4000/6000. The engine is an air cooled Lombardini 1 cylinder diesel.

 

Lister used to have air cooled marine diesels, my Dad had one on a yacht, the ducting came up through the deckhouse & out of the cabin top, he had a door on it to warm the cabin when needed, cold air came in via baffled vents in the front of cockpit, the exhaust was dry... all very reliable for years until the next owner put undersized corrugated flexible in place of the ducts... cooked it
A few local oyster barge tow boats had them too.

Jeff

 

I guess my favorite part of marine diesels, is having the wonderful world of on tap liquid for cooling.

 

Do not underestimate the increased NVH from an air-cooled engine. The necessary cooling fins create additional surface area to radiate noise. The necessary fan is a significant source of noise as well.
The significant heat thrown off is a serious issue as is the large and intrusive footprint and volume of the ductwork.

 

Water jacketed cylinders are much quieter, and all the shrouding surrounding an air cooled motor develops many rattles
Over time, and the air big blower creates noise too.
My hearing is now quite compromised from years of exposure to such sounds, so nowadays I go the extra mile to keep my boats sound levels down, so I can have conversations ( other than with myself) and keep a radio watch while under way.

 

I have a Finnish pilot boat with an air cooled diesel, Deutz 19 liter V12. The boats built for running in ice so the air cooling makes for a very simple cooling system without having to mess with clogged heat exchangers or strainers. And it’s nice to only have the propeller shaft to worry about with regards to seals and keeping water out of the boat.
The boat’s from 1966 and just about free from corrosion. Most likely to a large degree related to the ventilated hull and lack of sea water inside the boat. The air intake for the cooling is well protected from spray and the twin outlets are great for drying stuff.
Noisy? Not worse than similar output/displacement/rpm wet engines. That has, in my opinion, more to do with the boat than the engine.

 

Bet it is a Maximum Continuous Rating (MCR) issue; either that or an as supplied sump issue. Often disclaimers are based on things not under the manufactures control which could show the product in a bad light.

 

Air cooling on an ice boat sounds like a solid use. 300 hp out of 19 liters is not exactly setting the world on fire for performance numbers. Wonder what the air flow requirements would be in a warmer climate.

I'm over here dreading dry turbos on tier 4 generators, and lamenting how much longer lasting the water jacket setups were....

 

Sort of a branch off the original topic - are there many marine diesel engines and generators that have their own radiators and what I would call a closed loop cooling system? (rather than pulling cooling water from the ocean through the hull then through the motor and back out again?)

 

I've seen a couple. Lots of quasi passive keel cooled boats, essentially a through hull radiator.

In my neck of the woods I'd say 75-90% of the engines are keel cooled, with a closed loop going through some manner of coils like a Walter or rw fernstrum. My last boat actually ended up with keel cooled hydraulic oil as opposed to heat exchanger active cooled.

Keep in mind in the last two years I've only seen water Temps start with a 6 in degree f a couple times in the last two years. Aside from the blob years we don't see much over high 50s. That combined with lots of kelp and grass is a heavy motivator for closed circuit.

 

Lots of smallish (50-200 kW...so automotive sized) diesel gen sets in yachts are air cooled. But they need a lot of air...which can be generally found to keep the main engine room cool anyway. Main propulsion diesels....not so much...

 

We get to 65-68 degF here - that might prove to be a stretch for a keel cooler for us unfortunately judging by what you have said.

 

I would suggest that exhaust temps will make this a tricky installation in a boat, and potentially deadly via gases, fumes and fire. It is near impossible to have flexible exhaust components without raw water cooling, and if you're running a displacement raw water pump you may as well have the longevity, performance advantage and safety of a water cooled engine. If the cost of a heat exchanger is a problem, keel cooling is an extremely effective and cheap solution if the tubes can be protected, at least with water cooling there are no exposed red hot exhaust components. If insurance is necessary then an air cooled engine may not be acceptable.