engine heating and cooling

[prairietrawler]

I'm refitting an IH DT 466 Diesel engine into my '26 Tollycraft soon. I own a webasto diesel heater that I intend to use as an engine heater and also to heat hot water via a heat exchanger.
I currently have no heat exchanger or engine cooling gear of any sort. So I thought about a keel cooler for the engine, instead of a heat exchanger.
How should I set it up so the webasto-heated water can circulate thru the engine to keep it warm, and heat hot water, without heating up the whole ocean via the keel cooler.

I'm probably gonna need to buy a raw water pump to pump water to the wet exhaust so maybe I should use a heat exchanger instead.

What are the pro's and cons of each system ???


Thanks,

Brent

 

[Mischief Managed]

I did not know there were marine exhaust systems for the DT 466, where did you find the liquid cooled exhaust manifold?

I think that if you can find a coolant loop within the engine that that does not pass through the thermostat, the heater would work fine with keel cooling. My guess is that you could just use the heater hose ports since I'm pretty sure most engines only use the thermostat to block flow to the radiator, not the cabin heater. With that said, That engine should start up just fine in any temperature that allows for boating, why would you want to heat it?

 

[prairietrawler]

I'll actually build a water-cooled exhaust manifold, The runners from the cylinder head will be about 2" long before they enter the waterjacket to allow for bolting to the head.
I've talked myself into using a heat exchanger and various valves to manage the hot water flow to and from the webasto, the engine, the hot fresh-water tank and cabin heat exchangers.
Now I'm trying to size a raw water pump. Thru hull for intake is 1-1/4", but the intake strainer is 1".
will a 1 inch pump flow enough? I guess that depends on the speed it will run.
Wish me luck.

 

[O C Diver]

Most of the waterman on the Chesapeake come off the thermostat housing outlet to the keel cooler and back in at the freshwater pump, without requiring a second pump.

In your case, I would plumb a heat exchanger with the output unregulated by the thermostat and returning near the freshwater pump. Typically 3/4" hose would be more than sufficient. In that loop you would want to add a 5 GPM circulating pump designed for hot water. The pump will be needed to only preheat the engine off the boiler. Under engine operating conditions, the coolant will circulate with the freshwater engine pump.

On the other side of the heat exchanger would be your boiler, bus heaters and circulating pump.

Regarding pumps, I had great success with a March pump. The hot water pumps are magnetic drive (no shaft seal) and available in 12 VDC, 24 VDC, and 120 VAC. Mine was in the boat to boost the bus heater loop (100' +/-). I'm sure others are available also, but wanted something that was designed for continuous use.

March Pump

US Manufacturer Of Centrifugal Sealless Magnetic Drive Pumps for Chemical, Industrial, Medical, Marine, Solar, and OEM applications.

www.marchpump.com

The heat exchanger close to the engine will isolate the engine from all the heat loop failure points. I would also add quarter turn ball valves where the coolant leaves the engine and returns.

Here's the thread on my heating loop off the engine. While I didn't add a boiler nor needed to preheat the engine, you may find other information in the thread useful.

Cabin Heating with Engine Coolant (another project thread)

I've threatened several times to post this in totality, and am finally getting around to it. During my 2014 - 2015 refit I added a heating loop that runs off the engine's coolant system for heat while underway. So here are the details. Before I start, I should explain that I have CDO (Obsessive...

www.trawlerforum.com

Ted

 

[Jeff F]

Why do you want to heat the motor? Just curious.

I have a heat exchanger between my hydronic loop and engine coolant as Ted describes, but no pump as I only use it to capture engine heat while running.

I see the issue with preheating the engine with keel cooling. You lose the heat to the keel cooler. Pretty hard to do without working some valves. Why bother?

WRT marinization, have you considered a dry exhaust? If you're not bringing raw water in for cooling can you avoid bringing it altogether? With dry exhaust and keel cooling there's no marinization required for the engine.

 

[Portage_Bay]

With dry exhaust and keel cooling there's no marinization required for the engine.

It may not be required but it's a good idea use water cooled exhaust manifolds with dry stack to keep the exhaust manifold temperature to a safe level. Keel cooled or dry stack. I've run numerous work boats with dry stack, all of the engines, propulsion or generator, used water cooled exhaust manifolds.

 

[Jeff F]

It may not be required but it's a good idea use water cooled exhaust manifolds with dry stack to keep the exhaust manifold temperature to a safe level. Keel cooled or dry stack. I've run numerous work boats with dry stack, all of the engines, propulsion or generator, used water cooled exhaust manifolds.

In those cases it's coolant rather than raw water in the manifold, right?

Perhaps I misspoke on the marinization requirement, but I don't understand the need to have raw water input/circulation in addition to keel cooling. To my mind that's the big plus for keel cooling.

 

[Portage_Bay]

Yes it is engine coolant coolant in the manifold. Yes with keel cooling there is no need for raw water circulation.

 

[prairietrawler]

Ted. Much thanks. I knew this was being done, just never talked to a person who had at least see it done. I’ll chew on what you describe and consider my options.

 

[Lepke]

With keel cooling there's no salt water system. No pump, impeller, heat exchanger, seacock, hoses, to maintain. But within the coolant system the are usually dissimilar metals requiring protection. And depending on the keel cooler, hull material, some zinc protection for the cooler.
With a dry stack some fisherman build a section of pipe with a water jacket. Using a pump that creates a vacuum, and have a cheap watermaker. Water under a vacuum boils at a lower temp. The pipe water jacket needs a way of disassembling to remove the salt buildup.

 

[prairietrawler]

Thanks for all your input. I think what I'm wanting is:
An exhaust manifold cooled by engine coolant and dry exhaust. This will keep sea-water on the outside of the hull.
I'll circulate the engine coolant thru a heat-exchanger to make hot water and a bus heater for cabin heat.
I'll plumb a diesel webasto heater into this circuit to make heat when the engine doesn't run.
I'll use a Keel cooler, because they have no ancilary moving parts, but I'll isolate the keel cooler with a valve so I dont heat up the whole ocean when the engine is not operating.

Is this the simplest solution???

 

[Jeff F]

IMO you want two separate loops. One is engine coolant circulating through the keel cooler, and the other is heating fluid circulating through the Webasto, water heater and bus heater.

Between these two loops is a heat exchanger. When the engine is running you transfer heat from the engine coolant loop to the hydronic loop. When the engine isn't running you have no circulation in the engine loop, so there is minimal heat transfer from hydronic to engine or the keel cooler.

I ask again - why do you want to heat the engine with the Webasto?

 

[prairietrawler]

IMO you want two separate loops. One is engine coolant circulating through the keel cooler, and the other is heating fluid circulating through the Webasto, water heater and bus heater.

Between these two loops is a heat exchanger. When the engine is running you transfer heat from the engine coolant loop to the hydronic loop. When the engine isn't running you have no circulation in the engine loop, so there is minimal heat transfer from hydronic to engine or the keel cooler.

I ask again - why do you want to heat the engine with the Webasto?

Your idea makes sense. I never thought about a heat exchanger between the motor and and cabin heating. saves a bunch of valves!
In my mind starting a warm diesel is so much better than a cold start, and I was raised with Manitoba winters lol. Ya plugged everything in till July! That, I suppose, is why I want to heat engine with the webasto.

 

[keo1]

Ted - well done - a very informative article. There is a lot to consider when using the engine heat for heating of the boat. I used a heat exchanger in the cooling circuit on the volvo that is intended for heating as well. The risk factor is so much lower as the whole heating loop failure can result in serious engine damage. I used some BLDC pumps from aliexpress to aid in the circulation of the heating loop - some are listed as solar - but you want the automotive version as has a much greater temperature rating. Bleeding these systems to get the air out can be a real PITA - but the joy on a cold night when the whole boat is heated while underway is appreciated. We put a 10kw Eberspacher Hydronic in on the heating loop for hot water duty and heating when not underway. We cruise at 1350 RPM burning about 10 litres diesel. At that point there is more heat than you can use. Slow cruise up the channel at 700rpm takes more heat than is delivered - so engine temp drops a bit till the heat transfer process equalizes . Also on aliexpress is the floor heating manifold I used for all of the circuits. These have individual valves for all circuits and flow indicators - so you can really tweak the system. The project gets way more complex than you first envisage - there will be some revisions as you go due to the " learning curve" I used the PEX pipework as much as possible to reduce failures. Has been in for 8 years now and all still ok. But its all removable . That is one of the biggest lessons on boats - everything must be accessible. Still trying to work out how the Volvo comes out - has been in there for 43 years - but suspect either a chainsaw or a narrow gauge railway on the inside or both. K