Fresh Water Flush

[magna 6882]

Thinking about how i flushed outboards after each trip and was wondering if that would be practical or a wast of time. I have fresh water and the slip and was thinking i could pipe into the inlet water hose and add a thru hull on the pier side of the boat and simply flush after a trip. am i nuts? Your thoughts please.

 

[dhays]

Thinking about how i flushed outboards after each trip and was wondering if that would be practical or a wast of time. I have fresh water and the slip and was thinking i could pipe into the inlet water hose and add a thru hull on the pier side of the boat and simply flush after a trip. am i nuts? Your thoughts please.

I have been doing this for a couple years so I don’t think you are nuts. I did it the easy way and simply got a hose adapter for my raw water strainer. I attach the dock water to the raw water strainer and run the engine for 10 minutes at idle with the hose running and seacock closed.

Yes, it is a bit of a hassle, but I think it is worth it. If you have specific questions, let me know.

 

[BruceK]

We have a lightweight Mercury 3.3, no trouble taking it home after trips to flush run it in fresh water in a large container. Heavier outboards are more problematic, tough to lift,let alone transport to/from home.

 

[backinblue]

We have a lightweight Mercury 3.3, no trouble taking it home after trips to flush run it in fresh water in a large container. Heavier outboards are more problematic, tough to lift,let alone transport to/from home.

Or back to another topic, get an electric outboard. Lighter than gas, no flushing required! I put mine in a carrying case after using it and can toss it on a bunk or wherever is convenient.

 

[dhays]

We have a lightweight Mercury 3.3, no trouble taking it home after trips to flush run it in fresh water in a large container. Heavier outboards are more problematic, tough to lift,let alone transport to/from home.

I thought he was talking about doing a fresh water flush of the engine in his trawler, not the dinghy.

FWIW, most modern-ish outboards have a water inlet port to attach a hose to do a flush. If the motor is already up to temp, you shouldn’t even have to run it to flush it. Otherwise, run it at idle for 10 minutes to open up the thermostat.

 

[syjos]

I do'nt flush after every use but if the boat will not be used in more than a few weeks, I flush the engine and generator with fresh water.

When I go south for the winter, I fill the engine and generator with RV Antifreeze in case of severe freezing weather.

I flush using a Groco SSC Flush Adapter mounted on the seacock. Adding water at the seacock will fill the hose between the seacock to the strainer which is necessary when winterizing with antifreeze.

I avoid connecting dock water directly to the engine or generator for flushing. Some docks have very high water pressure, 60 psi or more, which could lead to leaks, cracks or a hose blowing off.

If I wanted to connect dock water directly to an engine, I would attach an adjustable water pressure regulator to the hose and set it for low pressure.

Brian at American Diesel does not recommend a direct connection for flushing Lehmans.

I do'nt use a regulator but do not attach the water hose from the dock directly to the flushing adapter. I attach a short hose to the flush adapter and place the open end of the hose in a bucket full of water. The water hose from the dock is placed in the bucket with water running to keep the bucket full of water. The engine or generator is then run a few minutes.

 

[Comodave]

I would be leery of hooking dock water directly to the wngines because of the pressure. I used a Sea Flush to winterize the engines in our last boat. It is simple to do, close the through hull, remove the top of the strainer and insert the Sea Flush into the strainer. Put the hose from the Sea Flush into a 5 gallon bucket and fill the bucket with fresh water then start the engine. Run for the desired time and shut it down.

 

[dhays]

I do'nt use a regulator but do not attach the water hose from the dock directly to the flushing adapter. I attach a short hose to the flush adapter and place the open end of the hose in a bucket full of water. The water hose from the dock is placed in the bucket with water running to keep the bucket full of water. The engine or generator is then run a few minutes.

This is an excellent point. One of the reasons I mentioned to ask me questions if interested. This is a very legitimate concern and as with most things, what works for one engine may not work for another.


As Syjos does, I think connecting at the seacock is a better way to go. I have yet been too lazy to change out the connection there so I just connect at the sea strainer. I also am not concerned about freezing so I don't winterize.


When I first did a flush, I did as Syjos does and connected a hose to the sea strainer and dropped it in a 5 gallon bucket that I filled with the dock hose. When the bucket was full, I started the engine, keeping the dock hose running fully open. I watched as the engine emptied the 5 gallon bucket in about 5 minutes even while the dock hose was running full blast.


This showed me that their was not a concern about pressurizing the cooling system of my engine with the dock hose. My next concern was that maybe I wasn't providing enough water. I checked with Tony Athens at SeaMar and his recommendation was that as long as the hose didn't collapse there was plenty of water available to the engine. That has been the case and I never have had a problem with the engine temp rising either, even after 15 minutes of running at idle on dock water.


If OTOH, the test with the bucket found that the engine couldn't keep up with the water from the dock hose, I would simply have flushed the engine while keeping the seacock open. Any extra water pressure would then leave via the seacock. That is in fact what I do with my genset when I flush it.


Here are the steps I use.
1. Engine off, seacock open.
2. connect the dock hose to the sea strainer.

3. Turn on the dock water.
4. start the engine.
5. close the sea cock.
6. run for 10 minutes.
7. Simultaneously shut down engine and turn on off dock water.
8. Open seacock
9. disconnect hose


#7 is key and I use a hose shut off valve inline in the hose that runs right by the helm so that I can do that easily.


Works for me. I do this every time I return to my home dock.

 

[cardude01]

Yeah I was thinking the same thing. I also use the bucket flush method.

 

[DennisB1]

I have the groco 1 1/4 adapter fitting on each cooling line to my Cat 3208ta. I hook up the hose and nozzle/shut off before starting the engines. The seacocks are closed when installing the hose attachment. Before starting an engine the seacock is opened and the engine run for a few minutes. Then its a trip into the engine room closing the seacock and opening the fresh water hose. I run the fresh water for about 5 minutes then shut down the engine and the fresh water at the same time. The raw water pump keeps up with the supply water and actually pulls a little vacuum on the line. This is visible when you watch the water in the glass chamber of the sea strainer (closed seacock). There is about 5 to 6 gpm water flow from the hose at about 70 psi source pressure. At idle 700 rpm there is plenty of water flow to keep the impeller lubricated and I have had no issues with impeller damage. There is a manual shut off on the engine which is used to shut down the engine along with those valve closure. Pressure is not an issue following this process as the flow from the hose is less than what would be normally flow on the saltwater side.

 

[Slowmo]

It sounds crude but our boat yard just turns a hose into the sea strainer (with the seacock closed) to flush the engines.

 

[murofrelwart]

I've found this article from Seaboard Marine to be very helpful:


https://www.sbmar.com/articles/the-benefits-of-fresh-water-flushing-your-marine-diesel-engine/

 

[DavidM]

It sounds crude but our boat yard just turns a hose into the sea strainer (with the seacock closed) to flush the engines.

That is essentially what I did, but a little more sophisticated with an elbow and valve tapped into the top of the strainer and a hose fitting. See attached pic.

David

 

[HeadedToTexas]

I do this every time I return to my home dock.

You flush the seawater out with freshwater from the dock every time you return from a run? On first blush and not being in salt water (yet), that seems like a lot. The more I think about it however, the smarter it sounds. Does everyone in salt water routinely flush their engine(s) with freshwater?

 

[HeadedToTexas]

I've found this article from Seaboard Marine to be very helpful:


https://www.sbmar.com/articles/the-benefits-of-fresh-water-flushing-your-marine-diesel-engine/

Excellent article and video. Thank you.

 

[backinblue]

That is essentially what I did, but a little more sophisticated with an elbow and valve tapped into the top of the strainer and a hose fitting. See attached pic.

David

Are you not worried about water pressure from the hose? Maybe I'm not fully understanding what you do. I read somewhere to leave the seacock open so excess water and pressure can exit, but the pump will still suck up what it needs for the engine.

 

[HopCar]

If you use the Groco adapter that Syjos suggested it can also function as a last ditch emergency bilge pump.
I had a way to divert my engine cooling pick up to suck from the bilge using two ball valves. I didn’t use it to flush the engine but it would have been easy to add that capability.

 

[lwarden]

I followed the SBMAR approach but did my own adapters into the tops of the sea strainer. I drilled and tapped in a 1" nipple and silver soldered it to the bronze cap. Then Groco ball valve and quick disconnect. I'm sure I'm still getting some salt water pulled through since the water needs of the pump are more than the hose can supply, but I imagine it's likely diluted by 50-75% which has to be a help. I could shut off the raw water but think the likelihood of screwing that up and leaving it closed and ruining an impeller aren't worth the risk. I also added flush connectors to the genny and cooling for the AC system.

The flush is pretty simple, I do it every time I'm not running it within a few days.

1. Start port engine
2. Go down and attach hose and run for 2 minutes or so
3. Go up and shut down port and start starboard
4. Go down and shut off hose, switch to starboard and let it run for 2 minutes
5. Go up and shut down starboard
6. Go down and remove hose
7. Double check both ball valve are closed
8. Go up and have a beer

 

[DavidM]

Are you not worried about water pressure from the hose? Maybe I'm not fully understanding what you do. I read somewhere to leave the seacock open so excess water and pressure can exit, but the pump will still suck up what it needs for the engine.

Here is how I use it:

Attach the water hose and open the fresh water valve with the seacock open. Start the engine at idle. Close the seacock. The raw water pump pulls more water than the hose can supply and it partially collapses. That is why you cannot leave the seacock open. With a bigger dock hose supply, maybe you could.

Then wait ten minutes. Close the fresh water valve and quickly shut the engine down. The reason you do it in this order is that you don't want water pressure on the raw water pump if the engine isn't running-could blow the seal. The few seconds that that there is no water flow won't hurt the impeller. Close the garden hose and open the seacock.

I did this for two years until I moved the boat to Connecticut where I was moored in the fresh water of the Connecticut River so I didn't need to do it any more.

Zincs lasted several times longer.

David

 

[Marco Flamingo]

All of the fancy connections to the seacock, or pouring water in the strainer, etc., and then running the engine seems way more complex than necessary, at least for my engine. I don't think my Lehman is all that different from other engines and I could flush it with a simple little fitting and skip trying to run the engine just the right amount of time or worrying about whether it is getting too much/to little water.

My raw water pump has a hose that goes to the first heat exchanger. If I put a three way barb right there, and the third barb went to a hose connection (capped off when not in use), I could simply hook up a hose there and use the dock pressure to clean out the entire raw water cooling system. I couldn't run it for too long or I might fill the exhaust lift muffler and up over the exhaust riser. But a 15 second squirt and I'd be done. I've seen some installations where the raw water enters the exhaust too close to the manifold and the engine has to be running to keep the water out, but that's not my situation.

Using a T connection after the raw water pump, I would not get fresh water back through the pump to the sea strainer, but that's not the concern of those who are concerned. It's the heat exchangers that might benefit from a freshwater flush during a storage period.

 

[DavidM]

Marco:

We have had a long discussion of these points over the years here and on boatdiesel. What you describe, introducing water after the pump impeller, works fine as long as, as you say, you don't fill up the lift muffler.

DAvid

 

[koliver]

Does everyone in salt water routinely flush their engine(s) with freshwater?

I haven't heard of anyone doing this, in over 45 years of saltwater boating, in a large Yacht Club where I have gotten to know a large number of boaters, ranging from the very casual to the very OCD.

This is not to say I disagree with doing this, just that it doesn't seem appreciated by the masses as something that is even a little helpful.

My own experience with the innards of my heat exchangers has been infrequent, and when I have had a peek in, has confirmed that they are not getting fouled by salt buildup to any noticeable degree.

 

[Marco Flamingo]

David,

I'll have to look, but I don't think that I could backfill up my exhaust to the point of causing trouble. My exhaust riser (shown here with the lagging removed) goes higher than my exhaust exit hose out the transom. Too much water might drain out the stern before it could get high enough to flood the engine. Don't know, but as Keith mentions, I'm not sure it's worth finding out. I just inspected my copper-nickel oil cooler and was surprised that it was perfectly clean. After seeing pictures on TF, I expected to find slime, seaweed, corrosion, and impeller blades.

My oil and transmission fluid coolers are copper-nickel without anodes. Both of them are fastened with a metal standoff from the block. But both had a wrapping of duct tape around the cooler where the metal standoff attached. All I could figure is that the tape was intended as electrical insulation. I've read on the web about people making sure that the heat exchangers are bonded to the block to prevent electrolysis. Seems like my prior owner came to the opposite conclusion. And it seems to be working.

 

[HeadedToTexas]

I haven't heard of anyone doing this, in over 45 years of saltwater boating, in a large Yacht Club where I have gotten to know a large number of boaters, ranging from the very casual to the very OCD.

I haven't either, but I am a novice and western Lake Erie is many weeks from the nearest salt water.

 

[psneeld]

I haven't either, but I am a novice and western Lake Erie is many weeks from the nearest salt water.

Ask around...after decades of running commercial and pleasure craft along the Eastern Seaboard....never seen anyone flushing standard diesels (Sea Ray gas I/Os yes though). At best, some may do it prior to winter layup along with an antifreeze flush.

Use Cupro nickel heat exchangers and the need falls way off.

Great Lakes? U less in a toxic waterway, seems like a waste especially in flushing with chlorinated city water which is bad like lightly sated salt water.

 

[syjos]

All of the fancy connections to the seacock, or pouring water in the strainer, etc., and then running the engine seems way more complex than necessary, at least for my engine. I don't think my Lehman is all that different from other engines and I could flush it with a simple little fitting and skip trying to run the engine just the right amount of time or worrying about whether it is getting too much/to little water.

My raw water pump has a hose that goes to the first heat exchanger. If I put a three way barb right there, and the third barb went to a hose connection (capped off when not in use), I could simply hook up a hose there and use the dock pressure to clean out the entire raw water cooling system. I couldn't run it for too long or I might fill the exhaust lift muffler and up over the exhaust riser. But a 15 second squirt and I'd be done. I've seen some installations where the raw water enters the exhaust too close to the manifold and the engine has to be running to keep the water out, but that's not my situation.

Using a T connection after the raw water pump, I would not get fresh water back through the pump to the sea strainer, but that's not the concern of those who are concerned. It's the heat exchangers that might benefit from a freshwater flush during a storage period.

Connecting dockside water directly to a Lehman is not recommended by American Diesel.

Using an intermediary bucket or a pressure regulator on the hose is suggested.

 

[syjos]

Flushing is not complicated.

I flush the Lehman and generator:

Warm up engine.

Shut off engine and close seacock.

Fill 5 gallon bucket with FW, leave hose from dock in bucket with water running.

Insert hose from the engine or generators Groco adapter into the bucket.

Start engine. I have a start button installed in the engine room.

The engine uses more water from the bucket than the hose from the dock can replenish it, so in about 2 or 3 minutes the engine is shut down before the hose from engine sucks air.

If anti freeze is required, pour antifreeze into bucket while engine is running, before the hose sucks air and shut engine off before bucket is empty.

The Groco adapters are mounted on the seacocks so the complete hose run from the seacock to exhaust is flushed and/or filled with anti freeze.

 

[syjos]

Every 5 years, the complete RW system is flushed with Barnacle Buster using the Groco adapter.:

A 5 gal bucket is filled with Barnacle Buster. There are other similar products out there that does the same thing like Salt Away and Rydlyme.

I remove the impeller and reinstall the pump cover.

Remove heat exchanger zinc. Barnacle Buster will erode zincs rapidly.

The hose from the engines Groco adapter is routed to a pump and the pumps inlet hose is placed in the bucket.

The RW hose from heat exchanger to the exhaust elbow is extended and directed to the bucket.

Barnacle Buster flows from the bucket to the pump and through the engine and coolers and returns to the bucket via the RW hose diverted from the heat exchanger

I run the pump for several hours checking the PH in the bucket every 30 minutes. When the PH reading stays consistent for 30 minutes, the RW system is clean.

Reinstall impeller and zincs.

The PH change is due to the calcium build up in the RW system dissolving in the Barnacle Buster and flowing into the bucket. When the calcium is gone and no more dissolved calciumn is flowing into the bucket, the PH reading in the bucket will stabalize.

I use an digital PH testor.

 

[DavidM]

Freshwater flushing was popularized by Tony Athens, first on boatdiesel and later on his own web forum at Sbmar.com.

One of the reasons is that the Cumins engine, which Tony promotes (not unreasonably) has a vulnerable sea water after cooler that needs regular maintenance attention. Fresh water flushing extends that maintenance interval according to Tony.

My Yanmar 6LY went ten years before I bought it and serviced the after cooler and it wasn't too bad. I think a Cummins after cooler would have been toast after ten years without freshwater flushing.

YMMV.

David

 

[Marco Flamingo]

Connecting dockside water directly to a Lehman is not recommended by American Diesel. Using an intermediary bucket or a pressure regulator on the hose is suggested.

I could see why it would not be recommended by American Diesel for the stock Lehman. The stock Lehman setup required one to run the engine to prevent raw water from flooding the exhaust manifold and draining into a cylinder. If one is flushing a stock Lehman with a hose through the raw water pump and running the engine, the pump could be partially starved if the freshwater supply hose didn't flow enough.

If the engine was run for more than a minute (why?) at idle with a reduced water supply from a FW hose, the engine exhaust hose might get hot. It wouldn't hurt the engine because the oil and water wouldn't even be warm yet. If one flushed for +10 minutes, then monitoring the water pressure would be important. I'm not sure of the benefit, if any, of long rinses. If introducing a specific strength of antifreeze, then a bucket method might be required.

But with an aftermarket exhaust riser like my Lehman, the FW hose would be connected with a T after the pump. Pressure wouldn't matter. No way to flood the exhaust manifold so no need to shut off the strainer, run a hose from a bucket, use a pressure regulator, and monitor them while running the engine.