Fresh Water Flush

[OBXSkipper]

I was over at the sbmar.com site checking out some of their videos , I came across the one that explains the benefits and pitfalls of a fresh water flush. Seems like a very simple solution to corrosion in any portion of a raw water/ saltwater cooling loop. Does anyone have one in use or had the opportunity to speak with someone does use one regularly ? Thanks

 

[rgano]

My boat came to me with tees in between the sea strainers for both the single 315 HP Yanmar and the Nextgen generator. The P.O. showed me how he ran both engines on freshwater with the boat in the maintenance skid before it was picked up by the forklift for restowing in the barn. He had owned the boat for five years, and I have owned it for seven. It now lives in a boat lift, and the engines are run on freshwater after every run down the bay. I also run some Barnacle Buster through the Yanmar's seawater cooling circuit every couple of years and only get some mild "browning" of the effluent collected in the recirculation bucket. I inspect the engine's anodes (zincs to some) at 2-3 month intervals rarely changing any except the one always submerged in the tranny oil cooler. All anodes are changed by the end of a year's time. I would have to say that based in the occasional removal of the oil cooler's end plate that the system is pretty clean.

 

[bshanafelt]

an additional 15 minute chore accomplished after any run in salt water.

 

[Pete Meisinger]

I did a simple do it yourself method. I tapped into a cold water line and added a short section of hose with a spray nozzle on it.

Certain aspects of it are a little on the gross side but it works great. It does use quite a bit of tank water, meaning a lot of black water goes into the holding tank. But it is a good simple solution.

pete

 

[firehoser75]

I was a follower of many of Tony Athens suggestions, especially the freshwater flush. It literally took me an extra 10 minutes to complete the task, from getting the hose out to putting it away. I connected the "garden" hose (5/8 inch) to the attachment on my strainer lid, and flushed for approx. 5 minutes with the engine running at idle. It was easy, worked well anytime the dock had a "reasonable" flow rate, and helps defer cooling system maintenance (and runs cooler between services as well) a couple of years. However, you will still need to do a complete cooling system service periodically (off engine with pressure testing of components), just less often.
The "payoffs" far outweigh any "extra" time put in!!!!
I would suggest changing engine anodes to aluminum (instead of zinc) if regularly freshwater flushing (or if you operate in both seawater and fresh/brackish water), as zinc develops a coating when exposed (sits in) to freshwater that impairs it's function as an anode. Aluminum does not and functions in both water types.

 

[Hyperion]

I was over at the sbmar.com site checking out some of their videos , I came across the one that explains the benefits and pitfalls of a fresh water flush. Seems like a very simple solution to corrosion in any portion of a raw water/ saltwater cooling loop. Does anyone have one in use or had the opportunity to speak with someone does use one regularly ? Thanks

Could you link to the info please. I have considered setting up a system for doing so.

 

[firehoser75]

Could you link to the info please. I have considered setting up a system for doing so.

https://www.sbmar.com/
There is a wealth of free info on the sbmar.com website under "Tony's Tips", and on the various forums. You can join the forum and ask questions, and receive answers. Sometimes from Tony himself.

 

[twistedtree]

I did a simple do it yourself method. I tapped into a cold water line and added a short section of hose with a spray nozzle on it.

Certain aspects of it are a little on the gross side but it works great. It does use quite a bit of tank water, meaning a lot of black water goes into the holding tank. But it is a good simple solution.

pete

I'm not following what you are doing. How does the water get into the holding tank? What do you spray to flush the engines?

 

[Comodave]

I'm not following what you are doing. How does the water get into the holding tank? What do you spray to flush the engines?

I was wondering that also…

 

[Hyperion]

I think he means head flush, with fresh water. I actually do that when I wash the boat after an outing.

 

[Chuck34]

I also have a garden hose connection on all my strainer lids, main engines, genset and air conditioning. I can flush any of them in a matter of minutes and winterizing is a piece of cake. I have a 3 gallon bucket tapped with a spigot, short hose to strainers, pour AF in the bucket, run the engine/AC for a minute, done.

 

[Comodave]

I also have a garden hose connection on all my strainer lids, main engines, genset and air conditioning. I can flush any of them in a matter of minutes and winterizing is a piece of cake. I have a 3 gallon bucket tapped with a spigot, short hose to strainers, pour AF in the bucket, run the engine/AC for a minute, done.

I used to do it that way when we stored in cold storage. Easy to do.

 

[Comodave]

I think he means head flush, with fresh water. I actually do that when I wash the boat after an outing.

Could be. I hadn’t thought about it that way.

 

[OBXSkipper]

Here is the link for the Fresh Water Flush info, several different options, all flush you motor with fresh water after use when at a dock or clean water source.
https://www.sbmar.com/articles/the-benefits-of-fresh-water-flushing-your-marine-diesel-engine/
Very Interesting and simple...Cheers

 

[Pete Meisinger]

Sorry, I was talking about flushing the toilet, not the engine.

pete

 

[2savage]

The major benefit of a final fresh water flush is the 'rotten egg' smell thing. Leaving sea water in the head will cause that ugly odor to permeate the whole boat.

I only have fresh water for the heads but with 1,100 gallons for the water tanks that makes it easier.

 

[Mischief Managed]

I recently added fresh water flush to both of my CAT 3208TAs. I did it with the boat's own fresh water system so that I can use it while away from the dock. My system is simply a Tee downstream of the strainer connected to a a ball valve that when open provides hot fresh water to my raw water pump. I use the sea cock for the engine to stop the flow of sea water and the ball valve to feed hot water. I also added starter and fuel stop switches to each engine in the engine room right by the valves and sea cocks so that flushing is really easy and convenient. I flush for 90 seconds per engine at idle speed. I use hot water instead of cold to stop condensation from forming on my after coolers, a known issue with the 375HP versions of 3208TAs.

 

[Greg QS]

I tied my water system int the engine cooling loop after the impeller. I have high lift exhaust with the shower head pointing down . This allows me to flush the system with fresh water while the engine is not running. I can also flush the stuffing boxes at the same time.

 

[Reef Wanderer]

Fresh Water Flush Ford Lehman

I have been freshwater flushing my Ford Lehman 120hp for the last 3 years, the results are that the heat exchangers are now always clean, with no sign of corrosion or calcium. I pull the anode in the main heat exchanger 2 monthly and wipe off the exterior as it does get a coating on it, probably from the fresh water, but it also had this when it was run only in salt water.
I should try the aluminium anodes to compare, but can't find them here in Oz.
I made my system simple, a 20liter plastic jerry-can fed with fresh water from boat tanks. A hose fitting in the lowest part of the jerry can with a 40mm hose fitted that tee's into the hose between the sea strainer and the raw water pump. Just before the T into the sea strainer is a large ball valve.
When I return from a trip (ocean water), I simply turn off the sea cock below the sea strainer (which I do every time I leave the boat anyway). Turn on a dedicated tap to fill the jerry can, till I see it is full. Open the ball valve to allow fresh water to flow into the raw water circuit, start the engine and watch as the fresh water level drops in jerry can, until I see bubbles in the hose feeding the raw water circuit, and push the off button on the engine injector pump. Then turn off the ball valve from jerry can.
All up takes me less than 3 minutes..... But saves me hours of cleaning/replacing/removing heat exchangers in the long term.

 

[Steve DAntonio]

I'm an advocate of fresh water flushing engines and gensets, however, keep in mind, when you so so, you expose the pencil anodes, if present, to fresh water. If they are zinc, they will develop a calcareous coating, which makes them go dormant. You can use aluminum anodes, they are immune to this issue, or remove the zinc anodes and clean them with a ScotchBrite every so often if you are FW flushing.

Groco makes a seacock that includes a flushing attachment, BTW https://www.groco.net/products/valves-seacocks/flanged-valves/sbv-series also good for descaling HVAC systems, with one on the intake and one on the discharge.

In Taiwan

 

[Bonedoc]

I added a flush this season. Groco T with valve plumbed to deck fitting.

I have 2 hoses dockside- I flush the motor with one as I post trip the boat with the other.

 

[Comodave]

I do a freshwater flush every time just by starting my engines…

 

[Hippocampus]

Steve what’s “every so often”? Monthly? Every 50 hours? Thanks

 

[mvweebles]

The SBMAR article shows an exhaust without a lift muffler (diagram attached for convenience), which works great when engines are installed near the transom. But for mid-vessel engine installs such as most trawlers, the exhaust systems have a lift muffler and a high-point (attached diagram from Northern LIghts "Please don't drown me" article). Wouldn't a pressurized water flush create a substantial risk of flooding the engine?

Peter

 

[OBXSkipper]

That is a great alternative, I was interested in the ease of installation of the screw on lid for the freshwater flush. Good info and great reminders on the Zincs ...Thanks !

 

[Bonedoc]

Mr Weebles yes there may be a concern there- thus I turn the fresh flow on/off only while engine is running. Per advice of Tony I never turn off the main SW seacock while afloat.

 

[lwarden]

I made a couple posts in another fresh water flushing thread previously but will summarize here.

1. The hose pressure is usually not near enough to compensate for the raw water pump draw so if you run with the seacock open you will still get a significant amount of salt water in the mix. In my case I shut the seacocks as so it's 100% fresh water. Of course you need to be very careful to open them up again...

2. I still am using zincs and they do create a coating when sitting in fresh water, but I've also seen this coating flush out when the engine is started normally so I don't think this is an issue. The solution here is to install aluminum anodes.

3. On my list to do is install a flush line with an overpressure relief valve (simple check valve) plumbed to the AC cooling sea strainer. That way I can shut each engine and the AC seacocks, turn on the hose and sequence each engine without worrying about over pressurizing any pump and while the engines are off it will flush the AC lines.

 

[OBXSkipper]

Peter good point to add to the discussion, did ya get a chance to take a look at his video on flushing, it was pretty informative on procedure. Perhaps if you had some really high pressure and volume at the dock it could be an issue. I don't have one in use so I can only speak hypothetically, perhaps someone who has one or something along similar lines could chime in and add some facts.

 

[mvweebles]

I had not watched the video when I posted but just did. He makes a point in the video that direct hookup of pressurized water flush is not for exhausts with lift mufflers, only with direct discharge. Rules out a lot of trawler style boats.

I also noted he recommends adapting elbows with tapped fittings to connect a hose (screenshots attached). The adaptation to the seacock elbow is especially concerning as it appears to make it vulnerable to side loading.

Freshwater flush is a really good idea, but there are some potential problems thqt could severely damage the engine so you have to be very careful. Would be a shame if when trying to extend the life of the engine you inadvertantly dramatically shorten it

Peter

 

[rgano]

Weebles, I believe a blanket statement that pressurized shore water rinse is not for vessels with lift mufflers should be taken with a very large grain of salt because conducting a fresh water engine rinse this way is all about method and technique. I have been doing this for seven years now with my Yanmar 6LPA-STP 315 HP engine with lift muffler, and two things I do not do are to shut off the seacock and leave the water pressurized when the engine is not running. As evidenced by the excess water running out of the seacock (boat is in a lift) with the engine idling and taking the water it needs to cool via the seawater pump, there is MORE than enough volume in the ordinary shore water connection to cool and rinse the engine without necessitating seacock closure. I shut off the freshwater supply to the engine as I am pressing the engine shutdown button. If your setup does not allow for these simultaneous actions, either don't freshwater rinse or arrange things so you can. Besides the obvious forgetfulness that could result in an seacock left closed, I am concerned about over pressurizing the seawater pump's water seal resulting in a leak there requiring pump repair.