Fresh Water Cooling System Flush

[Rick & Karen]

Good Evening All,

For those of us who operate our tugs in salt water, I learned a neat preventive maintenance tip yesterday while attending the Diesel in a Day course. The instructor, who works for the Yanmar dealer on island, said that heat exchangers and related cooling system components are one of the weak spots he sees when having to make repairs on engines that are overheating or have failed. Eventually the liner or mini radiator inside your heat exchanger will start to plug up and restrict the flow of cooling water. If you are lucky, the liner can be sent to a radiator shop to be boiled out and reinstalled. Anyway you look at it however, you will be spending a considerable amount of money making this repair. He showed the class a cast iron U-joint that is found between the heat exchanger and discharge hose that had almost closed up due to corrosion. The salt crystals that stay inside the heat exchanger every time you run the engine on your tug will accelerate this process.

To defend against this rather insidious process, our instructor said that some boat owners will install a valve or fitting that will allow them to flush out the raw water cooling system with fresh water. To my pleasant surprise, after studying the 8"x10" photos of my engine that I brought with me for reference, I realized that this feature was already installed on my boat. The R-21EC owner's manual makes a single refence in the to this feature on page 27 under Engines in the Winter Storage Checklist. It says to:

Flush sea strainer system with fresh water.

Now I apologize for perhaps pointing out the obvious to our more experienced boaters, but I did not make this connection until yesterday. We were told that if we flushed out the cooling system after every use, the corrosion process, would be severly curtailed. I tried it that evening after taking Kolo Iki out to secure the prop zinc and it worked exactly as described in class. I have never seen this issue addressed on this site or the C-Brats site so here are the (safe) steps for those that will want to try this on their boat:

1. Close the seacock to the sea strainer.

2. Unscrew the black cap on the T fitting installed immediately downstream of the sea strainer. A small amount of water will dribble underneath the engine and flow into the bilge. Attach a short section of hose to the threads on the fitting.

3. Fill a bucket up with about two gallons of fresh water and leave the running hose in the bucket. Place the end of the other hose you just screwed into the fitting in the bucket as well.

4. Start the engine and make sure that water is being drawn into the cooling system and discharged over the side.

5. Let the engine run for about five to ten minutes and then shut it down. Unscrew the short hose from the fitting, put the cap back on and you are done except for tidying up.

You can attach a garden hose directly to this fitting and not use a bucket, but I would caution against doing so with the following note.

WARNING: Do not attach the hose from your hose bib directly to this fitting and turn it on before starting the engine. Doing so may backfill the engine with water.

Personally, I prefer procedures that won't damage anything if I do something out of sequence.

The evidence presented in class made a believer out of me and I intend to flush out my raw water cooling system after every outing, just like you see people do with outboard motors. It only takes a few minutes and the potential cost savings and lack of downtime are significant.

Aloha,

Rick

 

[Tugly]

If you close the seacock completely, you run the small risk of allowing too much pressure being applied by the city water system. I close the valve about half way. Water will start to run out the intake when the hose is turned on. If that water stops when the engine is started, turn up the pressure a bit until a little water is coming out of the intake and you are assured that the engine is pumping under a nearly normal water pressure.

I usually run the engine about 15 minutes at a fast idle (about 1000-1200 RPM).

Bill

 

[rt11002003]

I didn't notice anyone mentioning it, but one can use that same fitting to winterize the raw water system.

I bought a washing machine hose, hooked it to the fitting in the raw water hose. Closed the raw water thru hull valve. Stuck the open end of the washing machine hose into the antifreeze container; started the engine and ran it until I got antifreeze coming from the hull exhause port, took about 3/4 gallon of antifreeze.

I also have a low pressure 110 volt pump that I can use for flushing or for winterization if for some reason I don't want to run the engine.

Gene

 

[Aintso]

Good One,

Many thanks for posting it. New to the inboard/diesel world so I appriciate these kinds of posts.

I'm all over this like a cheap suit.

Dave

 

[Rick & Karen]

Hi Bill,

You wrote:

"If you close the seacock completely, you run the small risk of allowing too much pressure being applied by the city water system. I close the valve about half way. Water will start to run out the intake when the hose is turned on. If that water stops when the engine is started, turn up the pressure a bit until a little water is coming out of the intake and you are assured that the engine is pumping under a nearly normal water pressure."

It sounds like you are describing this procedure while the tug is out of the water on the trailer using a garden hose attached to a hose bib. If you don't close the seacock completely while in the water, you will be diluting the fresh water with salt water. The hose in the bucket method ensures that the engine will draw what it needs. There was no appreciable difference that I could tell in the water volume coming out of the exhaust.

Regards,

Rick

 

[Kamalani]

Rick & Karen - I want to thank you for posting the info you learned in the one-day class. I wish I could have been there. I have been trying to figure out the fresh water flush process ever since we took delivery of our boat, and the little flush attachment was in the owner's kit. Yanmar's owner's manual makes no reference to flushing the cooling system, nor to a port or fitting. I am printing your post and will take it along next time as I rig a proper engine flush system. ( just to be clear, it is important not to apply hose pressure to the cooling system, but rather to allow the water pump to draw water from an open supply of fresh water??) Having this info makes me feel better about operating in salt water and taking proper care of the engine. Alex, "Kamalani"

 

[Rick & Karen]

Hi Alex,

You wrote:

"( just to be clear, it is important not to apply hose pressure to the cooling system, but rather to allow the water pump to draw water from an open supply of fresh water??)"

You are correct. As Bill mentioned above, if you are using the pressure off a hose and it is too high or if the engine is shut down while doing so, you can flood the internal parts of the motor and now you have a big problem. You can feel the suction from the end of the hose attached to the T-fitting while it is drawing from the bucket and if you are not adding fresh water to the bucket, it will empty out rather quickly.

An added bonus to this set-up that I didn't mention before is that you can also use this system while offshore as a very effective bilge pump if you have a hose onboard. It will pump a lot more water at cruise RPM than the electric pump in the bilge and it might mean the difference between coming back to port in a Coast Guard helicopter or your own boat.

Regards,

Rick

 

[Tom Ray]

As Bill mentioned above, if you are using the pressure off a hose and it is too high or if the engine is shut down while doing so, you can flood the internal parts of the motor and now you have a big problem.

That's one possibility, but it's also likely that an impeller blade would be folded backwards and get torn off.

I have flushed R-21's on the trailer by hooking up a hose and turning it on with the seacock open. Once the engine is running, quickly shut the seacock. Just before shutting the engine down, open it again. If you act quickly, there is not time at either end of the process for the engine to pull air from the through-hull fitting, so you can use it as a pressure relief.

Raw water pumps are effective bilge pumps, and some boats I have been on had a dedicated intake and a separate valve so that by closing the seacock and opening the valve, the engine would suck out any bilge water. Works great. Just make sure the bilge intake hose is upstream of a water strainer to catch any stray parts that may be in the bilge. Not that I've ever dropped anything into a bilge and been unable to get it back or anything... 😉

 

[Kamalani]

Thanks to everyone for the great info on engine flushing. Does anyone use an additive or engine flush product for routine flushing, or is fresh water good enough for this? Alex.

 

[Tom Ray]

I have never used one of the additives when flushing. My thought is that water does a pretty good job of dissolving salt without any help.

 

[Rick & Karen]

I have read on other boating forums that some boat owners have used a diluted solution of CLR (Calicum, Lime and Rust) available at Home Depot to flush buildups out of older engines. However, since my engine has just over 100 hours, I am hoping that any corrosion present is not very advanced at this point and fresh water flushes will be instrumental in keeping it that way. I tried using 1500 RPM yesterday and the flow of water passing through the heat exchanger was noticeably larger than at idle RPM.

I have posted a photo in my album under the Miscellaneous Items section showing the set-up that I am using. I wish I knew how Idle-Up is able to post photos inside the body of the posts 🙂

Aloha,

Rick and Karen

 

[HonuKai]

I've been wondering about this issue on my R25s. Andrew, Please ping in with some suggestions.
Thanks,
Tim

 

[Andrew Custis]

Well all of the engines we install are fresh water cooled. With this being said only one portion of the heat exchanger and the exhaust manifold sees salt water. The block is cooled with antifreeze. It is not nearly as critical to flush these fresh water cooled engines like it is in the older ones. By flushing the engine with fresh water you might extend the life of your exhaust manifold. That also brings up another point of how important it is to use the correct antifreeze in your engine. Every engine manufacturer suggest different types of antifreeze to be used. In marine environments they use a heavier duty antifreeze with extra corrosion inhibiters in it. Make sure to always follow what the engine manufacturer reccomends for types of antifreeze. Also a good idea to keep an eye on your engine zinc usually located in the heat exchanger. Bottom line is. If you want to flush your engine with fresh water, no problem at all. Most people that have fresh water cooled engines setting in the salt water do not flush their engine after each use. If you own a trailer and haul your boat out frequently then I think its a great idea to flush the engine with fresh water after each salt water use.


The non fresh water cooled engines would use the salt water throughout the whole engine and block to cool.

 

[HonuKai]

Andrew, First of all thanks for the reply. So, how does one go about flushing these R25s - short of a trip thru the locks and a ride in Lake Washington...?

thanks again,
Tim

 

[bluebayou]

HonuKai,
Briefly, there are at least two (2) methods of easily flushing out your seawater cooling system:
1) You can buy an inexpensive suction cup device at a marine supply store. It looks like a toilet bowl plunger, but you use it upside down, against your intake for the diesel. There's a place to attach a garden hose. Open the tap, check that the cup is properly sealed to the hull, and start your engine. The fresh water will spit out the sides. I do this on the trailer.
2) The other day, I watched a mechanic use a simpler method. He closed the seawater intake valve (be SURE to re-open it at the end of this process, or you will fry your engine next time !). Then, he opened the seawater filter (clear plastic, about 6 inches diameter). He inserted the end of a garden hose in there, adjusted the flow, and started the engine. The water could not take the easy path out the intake (valve closed) so it went through the engine jacket and out the exhausts.
Either one works fine, and, yes, you should do it every time the boat is hauled out of salt water. There is usually a hose bib available at the top of every Ramp, just for such purposes.

 

[HonuKai]

Bluebayou,
Some things are so obvious, you look right past them. I keep my boat in Puget sound and plan on hauling it every other year. Closing the seacock and putting a hose in the strainer seems the way to go. Thanks for the info.

Tim

 

[Kamalani]

Rick & Karen - I too was wondering how to insert a photo in a post. Someone came to my rescue a while back and suggested that the row of buttons atop the "post a reply" page contains a button labled "g2Img". That translates to "insert a Gallery 2 image". I have not tried this yet, but I believe that will be the answer to our question.
Alex. "Kamalani"
What the hey.... I'll try it here...

Woo Hoo!

 

[Rick & Karen]

Thanks Alex,

You learn something new every day 😀 On the gallery page I selected Image and 600x480 for the size to make the photo larger in the post.

 

[Tom Ray]

Alex, that's a great picture of Kamalani! Would you mind if I used it on our dealership website?

 

[Kamalani]

Tom - Cap'n. Sherry says "for a small fee"! Just kidding! We'd be honored to have "Kamalani" featured on your site. We are very proud of her, and always are amazed at the attention she draws. Alex & Sherry.