Antifreeze in Raw Water Side of Cooling System

wynkoop

Member III
For most of her life Silver Maiden had a raw water cooled Palmer P-60. Last winter/spring that was swapped out for a Yanmar 1GM10 which I put together a fresh water cooling system for. I have a heat exchanger from an old diesel generator, the raw water pump goes into one end of the heat exchanger and the other end goes to the exhaust fitting on the Yanmar. The cooling loop through the engine is filled with Dexcool and powered by a small electric pump.

I keep the boat in the water all winter. I sometimes like to go out in the winter. With the palmer I would suck antifreeze into the system when the weather got cold and if I went out after that I would just open the sea cock and go (used bio safe antifreeze).

I am wondering what folks do with the raw water side of their heat exchangers. I am thinking that I could easily drain the water out of the raw water intake line and the pump as well. Looking at things today I do not see an easy way to drain the heat exchanger. There is a valve on it, but mounting considerations forced it to be put someplace that is less than useful for draining and I am not sure if it is functional! The heat exchanger was a cast off at the boat yard.

Should I be looking at making sure I can drain it well, perhaps use my compressor to force water out, or should I suck antifreeze into the raw water side just as I did when I was raw water cooled? My other option is of course a some heater tape around the heat exchanger or an electric circulating heater in the fresh water side to both preheat the engine and keep the heat exchanger warm. I do not really like the idea of being dependent on electricity to keep my heat exchanger from bursting.
 

toddster

Curator of Broken Parts
Blogs Author
I have a simple Tee with a garden hose fitting on the water intake hose. A short piece of hose lives down in the bilge next to the valves. It takes about a minute to close the valve and suck up a gallon of antifreeze mixture into the engine and exhaust (I worry about the strainer and the exhaust standpipe freezing, as well). Some more expensive through-hulls are available with such ports built-in, or a 3-way valve might look better than the hose tee, but so far, the $1.50 solution has worked for me.
 

wynkoop

Member III
Yep toddster that pretty much mirrors what I had on the previous engine install. Guess I will put the TEE back on and suck antifreeze in figuring to blow it out again if I get underway. Was hoping to not go through a bunch of antifreeze, but I suppose one can never be sure of being completely drained.
 

nquigley

Member III
I have a simple Tee with a garden hose fitting on the water intake hose. A short piece of hose lives down in the bilge next to the valves. It takes about a minute to close the valve and suck up a gallon of antifreeze mixture into the engine and exhaust (I worry about the strainer and the exhaust standpipe freezing, as well). Some more expensive through-hulls are available with such ports built-in, or a 3-way valve might look better than the hose tee, but so far, the $1.50 solution has worked for me.
The picture shows my solution for winterizing with RV potable water system antifreeze (pink stuff).
The valve above the raw water strainer is attached to a ~6ft length of hose (pink) that carries antifreeze from its 1 gallon jug, through the strainer and into the cooling system. It remains loosely coiled in the space in the picture when not in use.
With the engine running, and the end of the hose at the bottom of the jug of antifreeze, one closes the raw water seacock and opens the valve (tan-colored handle), and then shuts the engine off when the pink antifreeze starts coming out with the exhaust.
The reason my hose is so long is so I can position the jug at the top of the companionway, where I can watch it from the helm (where the engine shut-off is). It takes a little less than one jug of antifreeze to go though the whole system.
Note: my boat is in the water year-round - we seldom remain below ~25F for more than a day or two. The first year I had the boat, I didn't do this step and we had about 5 days in a row below ~15F. ... the water in the strainer basket froze and cracked the strainer. So, it's strongly advisable to run antifreeze through the strainer too.

Another way is to close the seacock, open the lid of the strainer, and then continuously pour antifreeze into the strainer with the engine running - get someone to shut the engine off when antifreeze goes out in the exhaust.
IMG_4922.PNG
 

Filkee

Member III
The T is a nice feature. Right now I do the old 5 gallon bucket with a spigot gravity feed through the top of the strainer trick. It's never all that graceful but it gets the job done.
 

markvone

Sustaining Member
I close the hull valve and pull the raw water intake hose off and add an ~ 2 foot 3/4 inch hose extension which I stick directly into the 1 gal biosafe antifreeze bottle. Sucks about 1/2 gal for my Universal 5424. (24 hp)
Mark
 

Tom Metzger

Sustaining Partner
For once a year winterizing for -25*F I pulled the gosouta side hose off of the strainer, drained the strainer, and sucked a gallon of -50* antifreeze from the jug through the system and when empty I ran a gallon of -100* antifreeze through the system. This way eliminates filling the strainer with antifreeze. Opening the thru-hull after hauling drains the intake hose.
 

Kenneth K

Sustaining Member
Blogs Author
Antifreeze will pump purely through the small hoses and the heat exchanger, but once it reaches the lift muffler, it mixes randomly with the existing water in the muffler. May be best to drain the muffler first so the antifreeze doesn't get too diluted.

Or, use -100F antifreeze as Tom suggested, and it's still effective down to moderate temps even with dilution.

Also, not all "pink" antifreeze is "engine-safe." Some is just for potable water/head systems. I believe the "engine safe" stuff has corrosion inhibitors added.

I used a Groco SSC valve between the thru-hull and strainer. It has a removable plug that accepts a hose adapter for flushing or winterization.
 

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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Note that you are not introducing *any* antifreeze, pink or otherwise into the engine when you winterize the raw water part of your closed cooling system. This procedure is solely to protect the parts of the system, from thru-hull to HE to muffler to exhaust outlet - anywhere water will normally sit when the engine is off - from freezing.
 

Tom Metzger

Sustaining Partner
Antifreeze will pump purely through the small hoses and the heat exchanger, but once it reaches the lift muffler, it mixes randomly with the existing water in the muffler. May be best to drain the muffler first so the antifreeze doesn't get too diluted.
This is why the -50* gallon first, to clean out the water. It costs $2.50 - 3.00/gallon. The -100* costs 3 - 5 x as much, and you have to have -50* for the water system so it's available.
Also, not all "pink" antifreeze is "engine-safe." Some is just for potable water/head systems. I believe the "engine safe" stuff has corrosion inhibitors added.
As Loren points out the raw water system is not the engine. Corrosion during the winter is not really a problem. I've even heard of people who use salt water to cool their engines in the summer. Go figure...
 
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