Keel Cooled and Dry Exhaust

[Lucy 11]

My education continues!!! The Allweather I'm very close to purchasing has a Keel Cooled/Dry Exhaust set-up ........... I've googled and have a general idea how this system works however I'm sure that there are contributors who would like to comment and point out the pros/cons of this set-up......... much appreciated.... john

 

[Delfin]

My education continues!!! The Allweather I'm very close to purchasing has a Keel Cooled/Dry Exhaust set-up ........... I've googled and have a general idea how this system works however I'm sure that there are contributors who would like to comment and point out the pros/cons of this set-up......... much appreciated.... john

That is the setup on Delfin. Pros are simplicity, no sea water entering the vessel and a cooling system entirely protected by coolant, so no zincs, corrosion, etc. Cons aren't many, perhaps just some trade offs. The keel cooler could be damaged if you hit something, although that is a function of poor design. If the vessel sits for awhile and depending on the motor, soot can be ejected on startup, but I have only had this be an issue once in 5 years, so it hardly qualifies as an issue, and can be reduced pretty significantly by running the engine up to 90% of WOT for 5 minutes about 15 minutes before shutdown. On Delfin, one mistake I made is not cocking the exhaust stack 30 degrees or so off to one side. The result is that I get exhaust soot on the mizzen mast. All that means is that I have to wipe down the mast instead of the hull, and I could have largely prevented the problem if I built the stack slightly differently.

Most commercial boats will be dry exhaust because the design is simpler with less to break.

 

[swampu]

Using the keel cooler you need to use 1/2 antifreeze and water. Put a bucket over the drystack so you don't get blowing rain in your exhaust. Other than that your good to go.

 

[Delfin]

Using the keel cooler you need to use 1/2 antifreeze and water. Put a bucket over the drystack so you don't get blowing rain in your exhaust. Other than that your good to go.

And if a bucket over the stack isn't yachtie enough for you, one can build a faux stack that serves the same purpose. Here is a drawing of the one I designed and had built for Delfin.

 

[Lucy 11]

bucket man

I'm a bucket kind of guy BUT your plan will go into the file for future reference .... looks like it would be very functional AND it would look a lot better than the bucket ------ many thanks for your input... much appreciated,,, john

 

[Scary]

Question with Keel cooler

How is the fuel, engine oil , and transmission cooler feed with coolant. I would think that a closed system wood run hotter than a sea water cooled system as most times coolers cool with sea water in front of the closed cooling system?

 

[swampu]

I have a transmission cooler in the series for the transmission. Coolent is pumped through a shoebox size heat exchanger. The fuel just gets hot and returns to the tank were I would consider that a heat sink unto itself. (250 gallons) The engine oil is cooled using a cooler, attached.

As long as you don't get to much build up on your keel cooler and it's sized right you shouldn't have any problems. And no sea water in the boat. Delfin, here is a picture of my "bucket" It works great and seam to be a series of pipe cut and welded to get a false stack and a much needed over hang. The only thing that gets me when tied to the dock and cold starting in the winter (stern faces north) I usally get a smoke out in engine room because the wind blows the white smoke back down the outer tube. I was going to get a steel plate fab'ed to block it off but the air flow is probably good for cooling the muffler. I don't know.

 

[Delfin]

How is the fuel, engine oil , and transmission cooler feed with coolant. I would think that a closed system wood run hotter than a sea water cooled system as most times coolers cool with sea water in front of the closed cooling system?

I think if the keel cooler is properly sized, they work as efficiently as they need to, just as a radiator works on a truck. On the CAT, the transmission oil goes through a heat exchanger that has engine coolant running through it. I don't think this engine has a separate oil cooler, but I'm not sure....

If you keep maintained coolant in a closed loop keel cooled engine, you eliminate a whole raft of other maintenance issues and failure points of a sea water cooled engine. If you're thinking about a sea water cooled engine through a heat exchanger, that seems like a system where the keel cooler is simply mounted internally, opening up separate maintenance issues.

 

[Delfin]

I have a transmission cooler in the series for the transmission. Coolent is pumped through a shoebox size heat exchanger. The fuel just gets hot and returns to the tank were I would consider that a heat sink unto itself. (250 gallons) The engine oil is cooled using a cooler, attached.

As long as you don't get to much build up on your keel cooler and it's sized right you shouldn't have any problems. And no sea water in the boat. Delfin, here is a picture of my "bucket" It works great and seam to be a series of pipe cut and welded to get a false stack and a much needed over hang. The only thing that gets me when tied to the dock and cold starting in the winter (stern faces north) I usally get a smoke out in engine room because the wind blows the white smoke back down the outer tube. I was going to get a steel plate fab'ed to block it off but the air flow is probably good for cooling the muffler. I don't know.

When it rains, where does the water go? Or do you have an exhaust cap? I had one, but it made a racket at idle so I built the faux stack I showed.

 

[swampu]

When it rains, where does the water go? Or do you have an exhaust cap? I had one, but it made a racket at idle so I built the faux stack I showed.

I don't have a good picture of the design but ultimately it looks like your design but with the final exit point horizontal. The small "actual" exhaust pipe is about 4 or 5 inch and the faux pipe is about 8 or 10 inches. That keeps the actual pipe from touching any wood going though the roof and the final bend on the faux pipe is about 1 foot so the rain is minimal. The only issue I ever have is when tied to the dock and starting up if the wind is blowing from the aft I'll get a little blow back on the smoke. I'll take some pictures today and try to post them up. I like your design, how does it work?

 

[Nomad Willy]

Dry stack systems aren't limited to large boats at all. Here is the "stack" on a friends Willard 30' Voyager.

 

[Delfin]

I don't have a good picture of the design but ultimately it looks like your design but with the final exit point horizontal. The small "actual" exhaust pipe is about 4 or 5 inch and the faux pipe is about 8 or 10 inches. That keeps the actual pipe from touching any wood going though the roof and the final bend on the faux pipe is about 1 foot so the rain is minimal. The only issue I ever have is when tied to the dock and starting up if the wind is blowing from the aft I'll get a little blow back on the smoke. I'll take some pictures today and try to post them up. I like your design, how does it work?

Seems to work ok. I don't see how any water can get into the main exhaust stack, and it looks good, or at least appropriate for the vessel.

 

[FF]

I think if the keel cooler is properly sized, they work as efficiently as they need to, just as a radiator works on a truck

"Proper sized " will usually be for a worst case Tropical warm water at full rated load.

Since this is overkill, or over cooling , for best operation a by pass thermostat is required between the engine and keel cooler.

This operates in the 50/50 coolant solution so there is little extra maint , tho they cost about $400 for the complete kit in 1 1/2 inch ( a common) size.

Cooling the exhaust manifold and oil and tranny are usually all part of the coolant ,circuit and require no extra concern.

For folks that operate in freezing conditions KK and DRY is the only rational choice.

Otherwise you must winterize the sea water side every time you shut down.

 

[Phil Fill]

When we bought the Eagle had dry exhaust, which we changed to wet as the dry make the hot exhaust pipe make the engine room, salon, and lazaretto to hot and noise. Converted to a modified water lift muffler that is self draining, which cooled and quieted the exhaust. At least I do not glow, look like Alice Cooper, when checking the engine room. The Eagle exhaust could still be dry by opening an above water though hull, which I did once but the exhaust was still to hot/warm, so its been wet every since. Next pull I am going to take out and fill in that above the water line though hull. . I hate through hulls and took out all the through hulls below the water except the two in take for the gen set and main.


Most of the commercial trawlers are keel cooled, and dry exhaust. Again I would not have keel cool as the tubes are exposed and usually covered with growth. Yuck! I hate grow on the hull as I have a diver twice a year check/clean the hull. True no sea water gets inside the boat, but there are still two though hulls that could fail, and if the coils fail the only way to repair is pull the boat

Anyway, I think there are just as many cons as there are pos! If the boat already is keel cooled with dry exhaust you could still change the exhaust to let the sea water cool/quite and still be dry exhaust.


So is the gen set also keel cooled and dry?

 

[Sailor of Fortune]

Just curious if you still have your Allweather boat and how you like it.

 

[FF]

'Most of the commercial trawlers are keel cooled, and dry exhaust. Again I would not have keel cool as the tubes are exposed and usually covered with growth. Yuck

Most external keel coolers are on retrofitted boats , not new builds.

On steel boats a box is welded internally with fences inside to guide the water .

These are sized for worst case tropical waters , full rated load and growth on the hull.

Smooth on the bottom , but gen sets can grow extra dirty from the heat

IF I were specking a new build cruiser , KKDS (keel cooled dry stack) would be ONLY choice.

.Lived with both systems , would never go back!

 

[ak-guy]

Just curious if you still have your Allweather boat and how you like it.

I have an Allweather and it is keel cooled with dry exhaust. I like it for its simplicity and currently with the temperatures around 10F I don't ever have to worry about anything freezing. The engine is original and was designed to be raw water cooled so the running temperature is only around 130F. It would be nice to have more heat for the cabin. I did upgrade the exhaust with a much better muffler. It is still a fairly noisy boat but has been improved a lot with insulation etc.

 

[sunchaser]

Be careful on not winterizing a keep cooled vessel especially one that goes on the hard in northern climates. Not only are the genset, water systems and RO units able to freeze, but so are unchecked engine coolant systems that have developed a leak and get inadvertently refilled with fresh or seawater.

 

[Maerin]

The engine is original and was designed to be raw water cooled so the running temperature is only around 130F. It would be nice to have more heat for the cabin. I did upgrade the exhaust with a much better muffler. It is still a fairly noisy boat but has been improved a lot with insulation etc.

With the engine being keel cooled, what would be the problem with changing the thermostat to a higher setting? My understanding is that thermostats with lower settings are used in engines with seawater heat exhangers to minimize precipitation of the minerals in the seawater, thus extending the service interval of the exchanger. Since yours has no seawater exchanger, that reasoning doesn't apply. The diesel would probably like a higher run temp, anyway, and that addresses your cabin heat issue at the same time. My Cummins is keel cooled, the thermostat is set 193F. May be worth checking with a diesel pro.

 

[ak-guy]

Be careful on not winterizing a keep cooled vessel especially one that goes on the hard in northern climates. Not only are the genset, water systems and RO units able to freeze, but so are unchecked engine coolant systems that have developed a leak and get inadvertently refilled with fresh or seawater.

No genset, fresh water system drained, engine coolant checked/tested.

Maerin: "With the engine being keel cooled, what would be the problem with changing the thermostat to a higher setting?"

I did look into this and one issue was the rubber impeller water pump. My engine uses the original raw water pump to circulate the coolant. I was told that the rubber impeller will not last with hotter antifreeze/water mix. I haven't had this confirmed from another source. Also I don't want to open up a can of worms with alternator temps, exhaust flue temps etc. Perhaps the higher temps are not a problem I don't know. This engine has two thermostats for some reason and I haven't researched very much but have been unable to locate higher temp versions.

There was a suggestion to install some kind keel cooler bypass line with a valve or thermostat but that sounds tricky to me.

 

[Xsbank]

What kind of engine uses a rubber impeller as a circulation pump?

All you need to do is use the engine driven pump to circulate the coolant through the keel cooler. A hotter thermostat will heat the engine higher until the thermostat opens and it circulates through the cooler, just like a car with a radiator.

 

[C lectric]

Raw water cooled engines run cold for a reason. The reason is when the seawater gets to something over ~140oF the salt in it will start to plate out on the metal surfaces FAST. If you want to plug your engine's cooling passages that's a good way. Leave the cool thermostat alone unless it physically starts to give trouble. Then replace it with another of the same.

It might work if you get a large or oversize bus heater that can use the lower temp, 130oF, water. 130o water will still provide a lot of heat, it will just take a bigger radiator to scavenge enough heat.

OR If you want heat get a proper cabin heater such as a small bulkhead diesel unit, small diesel stove, or similar

But do not raise the engine temperature.

 

[ak-guy]

What kind of engine uses a rubber impeller as a circulation pump?

All you need to do is use the engine driven pump to circulate the coolant through the keel cooler. A hotter thermostat will heat the engine higher until the thermostat opens and it circulates through the cooler, just like a car with a radiator.

There is no engine gear driven pump as it was a raw water cooled engine. Only a belt driven impeller (raw) water pump.

 

[ak-guy]

Raw water cooled engines run cold for a reason. The reason is when the seawater gets to something over ~140oF the salt in it will start to plate out on the metal surfaces FAST. If you want to plug your engine's cooling passages that's a good way. Leave the cool thermostat alone unless it physically starts to give trouble. Then replace it with another of the same.

It might work if you get a large or oversize bus heater that can use the lower temp, 130oF, water. 130o water will still provide a lot of heat, it will just take a bigger radiator to scavenge enough heat.

OR If you want heat get a proper cabin heater such as a small bulkhead diesel unit, small diesel stove, or similar

But do not raise the engine temperature.

It is a keel cooled engine that was adapted from a raw water cooled engine.

 

[C lectric]

Ok, understood. Then you should be able to use a hotter thermostat.

Yeah, I read the keel cooler bit but didn't pay enough attention.
Sorry, cranial cramp.

 

[FF]

"I did look into this and one issue was the rubber impeller water pump. My engine uses the original raw water pump to circulate the coolant. I was told that the rubber impeller will not last with hotter antifreeze/water mix."

If your engine is keel cooled it will never have seawater inside.

The thermostat can be changed to hope to increase the water temperature , BUT the cold water returning from the cooler may be so cold that the engine can not get to say 180 unless at high load.

The cure is the bypass thermostat which is only 3 hose connections.

Rubber impeller pumps can suffer from higher circ water temps , but have no problems with antifreeze.

The solution for the impeller pumps is to install 2 or 3 gaskets , so the impeller is not bound when circulating hot water.

 

[Ski in NC]

The impeller may not like 180F coolant, but generally it will be drawing from the outlet of the KC where coolant is much cooler. Impeller should not see 180F. Now if you rig up a bypass to keep engine coolant circulating, then impeller will see some heat. Should still be ok.

I doubt that Yanmar will suffer at all keeping the stock 140F tstat. It was designed to run at that temp and it will be thrilled to pieces to have coolant in it vs sea water!!!

Also there are some mfr's of belt driven centrifugal pumps, like Oberdorfer used on old Onan 15kW gennies. Pretty small pump, but might be worth a look.

 

[ak-guy]

The cure is the bypass thermostat which is only 3 hose connections.

I have had this mentioned before but I don't know what it looks like or where to get the parts to set it up. Is it a stock housing for a thermostat?

 

[Xsbank]

My understanding of my keel cooler is that the engine runs with the thermostat closed until the correct temperature is reached (Cummins has two thermostats side-by-side, which is annoying as they are expensive) then the thermostat opens and allows some cold keel-cooler coolant into the system to maintain the operating temperature. When the thermostat is fully open, the keel cooler coolant circulates directly throughout the engine. There is no heat exchanger. If I am running at reduced rpm I will not be circulating all the coolant through the engine as the thermostat will start to close to maintain operating temperature. There is one pump only, the engine-driven one mounted on the front of the engine, the same as a truck. The keel cooler is just like a radiator in a truck, it is useless until the engine reaches warmer temps and the thermostat begins to open and circulate coolant through the radiator.

The thermostat opens gradually and modulates the temperature, it does not open and shut like your refrigerator door.

It also explains why I need a multi-gallon overflow tank when I run high (2100) rpms because of the expansion of almost 200 litres of coolant.

Also, make sure you test the coolant regularly for the condition of the additives in the coolant; when they become diminished your engine (diesel) is at risk. Some coolant filters also include additive packages so don't be shy about changing them. Most diesel places will sell you test strips.

If I am wrong with this scenario, please enlighten me.

 

[Delfin]

My understanding of my keel cooler is that the engine runs with the thermostat closed until the correct temperature is reached (Cummins has two thermostats side-by-side, which is annoying as they are expensive) then the thermostat opens and allows some cold keel-cooler coolant into the system to maintain the operating temperature. When the thermostat is fully open, the keel cooler coolant circulates directly throughout the engine. There is no heat exchanger. If I am running at reduced rpm I will not be circulating all the coolant through the engine as the thermostat will start to close to maintain operating temperature. There is one pump only, the engine-driven one mounted on the front of the engine, the same as a truck. The keel cooler is just like a radiator in a truck, it is useless until the engine reaches warmer temps and the thermostat begins to open and circulate coolant through the radiator.

The thermostat opens gradually and modulates the temperature, it does not open and shut like your refrigerator door.

It also explains why I need a multi-gallon overflow tank when I run high (2100) rpms because of the expansion of almost 200 litres of coolant.

Also, make sure you test the coolant regularly for the condition of the additives in the coolant; when they become diminished your engine (diesel) is at risk. Some coolant filters also include additive packages so don't be shy about changing them. Most diesel places will sell you test strips.

If I am wrong with this scenario, please enlighten me.

That is the way mine works on our CAT.