Keel cooler maintenance

[Vahevala]

We have a keel cooler on our 52’ steel hull trawler. We haven’t been able to locate any information about maintenance schedule as to how often it should be removed, cleaned, drained, refilled. Previous owner notes he had it removed, small pinholes repaired, drained and refilled in 2017. Guessing probably needs to get done, but really have no idea!

 

[DCDC]

What type of coolers? Steel hulls may have yard-fabbed half or full pipe exchangers. We have two Fernstrum cupronickel models. The only maintenance needed in the last 5 years was scraping away barnacles (in or out of the water) and changing zincs.

If you are not losing or gaining coolant then there are no significant holes. Identifying small holes or cracks is best done after removing them and pressure testing or using dye penetrant testing. I would not trust welding unless you can verify the welder has experience and equipment for your exact material of construction.

Coolant replacement can be done in or out of the water. Easier if on the hard as the cooler drains will be the low point. In the water change is tougher as it is difficult to remove the old coolant without repeated flushes.

Good luck with your coolers.

 

[Lepke]

I had a number of commercial boats with keel coolers. I was in the North Pacific so cool waters. I never had growth a pressure washer couldn't remove. I never had known leaks, but commercial coolers are heavier built. Other than zincs and haulouts, I did no maintenance.
Steel boats coolers were usually built into the hull and painted. Some were copper/nickel. One wood boat was copper pipe.

But back then you could buy bottom paint that actually did its job.

 

[twistedtree]

I had a furnstrum cooler on my last boat. The zincs needed to be replace surprisingly often. 9-12 mo max as I recall. Otherwise clean the tubes whenever you clean the bottom. Getting behind the tubes can be tricky.

Since there is a history of leaks, I would put the coolant on an annual fluid analysis program to monitor for seawater contamination.

 

[OldDan1943]

My N46 had a kell cooler. Whenever I did the bottom painting, I would remove it, sent it to a radiator shop that "knew" about keel coolers, Had it cleaned and pressure tested. The key is to replace the gasket with a new gasket when reinstalling it. I would put in New/fresh coolant each time. Never had a problem after the first time. The first time it really needed cleaning. I did not paint it.

 

[IRENE]

We also have a Fernstrum Gridcooler. It was last removed from the boat in early 2018. It has been out of the water for a visual exterior inspection annually.

We paint the bottom every 2 years. On those years the cooler gets an extensive cleaning. Our diver scrapes it regularly. Neither the out of the water cleanings nor the diver get more than 75% of the thing clean, you just can’t access all of it. So there is some build up over time.

Next year, we will remove it completely and send it to a radiator shop for a thorough cleaning in and out, and pressure testing. I do not believe ours has ever been professionally done…its been in service since 2011.

 

[OldDan1943]

Paint insulates the the keel cooler and reduces efficiency so unless that is taken into the design, what is the wisdom of painting the keel cooler? I never had a buildup on the cooler.
On my N46, the keel cooler was tucked into a hull pocket to give it maximum physical protection.

 

[Hippocampus]

I’m curious. If building in aluminum would it be possible to have the cooler enclosed inside a separate compartment as part of the keel which was flooded by coolant? Aluminum conducts heat well. If in a separate compartment heat expansion could be dealt with. Thermal coefficient would be the same as the same coolant would be used for the bath as well as in the pipe. Only part exposed to seawater would be the same Al as used for the hull. With no piping exposed maintenance would be minimal.
Your thoughts?

 

[Vahevala]

Thanks all, sounds like we should be ok until next haul out, and we’ll have a close inspection done at that point. We are fairly certain this keel cooler is built in to the hull, as our boat is a custom build from Vancouver B.C. It is in a pocket, and follows the lines of the hull but is fully protected. Excellent plan to have the coolant checked for salt water intrusion.

 

[Vahevala]

We think they are custom made, they fit right into the hull. Next haul out will be a closer inspection. Lots to learn on this boat, trying to increase our learning curve all the time!

 

[OldDan1943]

Please remember, you will need new gaskets!!!!

 

[Lepke]

Aluminum works fine as a boxed in keel cooler. You coolant needs to be what runs in aluminum engines or radiators. On fishing boats the keel is usually an I beam and boxed in with plate the same size as the hull plating. Some use one side for the main and the other for a generator. On longer boats it's divided into sections for the various engines. A few share the keel cooler with all their engines, but not an idea I like. The only boat I saw with that setup had a terrible time balancing the engine heat, but had a full time engineer.

Boxed in keels usually last the life of the hull if maintained. If you build one, put a drain at each end so it drains completely no matter how the hull is blocked.

People paint keel coolers because they're not all made of metal that inhibits marine growth. And in commercial boats they're built with excess capacity.

 

[Hippocampus]

Thanks L good to hear. Solves the maintenance issues while still having the benefits of a dry stack.
Similarly not a fan of marelon. Don’t understand why standpipes, and seachests aren’t the de rigor on Al.

 

[Vahevala]

Old Dan:Ok…I guess we would need to take the old gaskets off and figure out what to get??? Are the gaskets for the drain plug? Also, there is no mention of zincs for this system by the P.O. or the divers who have attended to the bottom.

 

[OldDan1943]

The gaskets?
the one at the joint between the keel cooler and the rest of the cooling system