Fresh Water Flushing -- Water Supply Question

[Markai6768]

I am considering trying regular (every time I return to port) fresh water flushing, but I have a concern that I hope you might be able to help me address.

I have a fresh water garden hose connection to the top of the Groco Sea strainer assembly (from Seaboard Marine) for fresh water flushing that should work quite well.

https://www.sbmar.com/product/groco-arg-series-bronze-cap-with-freshwater-flush/

However, when I connect my fresh water supply hose to the bronze fresh water flush cap, at idle (Cat 3126 engine), and begin to close the through hull raw water supply I can see bubbles forming throughout the water canister of the Groco sea strainer.

This raises the following questions:



1). I worry that I might be supplying insufficient water supply to properly lubricate the Sherwood (engine driven) raw water pump? Is this concern reasonable when the Sherwood pump is being supplied at idle by an average garden hose water supply?

2). Since the fresh water garden hose supply volume is clearly less than the water supplied by an open through hull, am I at much risk of contributing to engine and wet exhaust component overheat IF I run the engine at idle for approximately 5 minutes?

3). When you fresh water flush, do you leave the through hull open and put up with a mix of sea water/fresh water, or do you close the through hull to achieve 100% fresh water supply?

Cheers...

Marcus

 

[Comodave]

I am considering trying regular (every time I return to port) fresh water flushing, but I have a concern that I hope you might be able to help me address.

I have a fresh water garden hose connection to the top of the Groco Sea strainer assembly (from Seaboard Marine) for fresh water flushing that should work quite well.

https://www.sbmar.com/product/groco-arg-series-bronze-cap-with-freshwater-flush/

However, when I connect my fresh water supply hose to the bronze fresh water flush cap, at idle (Cat 3126 engine), and begin to close the through hull raw water supply I can see bubbles forming throughout the water canister of the Groco sea strainer.

This raises the following questions:



1). I worry that I might be supplying insufficient water supply to properly lubricate the Sherwood (engine driven) raw water pump? Is this concern reasonable when the Sherwood pump is being supplied at idle by an average garden hose water supply?

2). Since the fresh water garden hose supply volume is clearly less than the water supplied by an open through hull, am I at much risk of contributing to engine and wet exhaust component overheat IF I run the engine at idle for approximately 5 minutes?

3). When you fresh water flush, do you leave the through hull open and put up with a mix of sea water/fresh water, or do you close the through hull to achieve 100% fresh water supply?

Cheers...

Marcus

At idle a garden hose should supply enough water.

Close the through hull.

 

[HopCar]

My first thought was to agree with Comodave, but the bubbles bother me. I don’t think they are air bubbles but vacuum bubbles because the engine is pulling water out faster than the hose can supply it. The adapter does constrict what the hose can supply at least a little. My guess is that running for just a few minutes won’t be a problem but you might want to ask Seaboard Marine.

 

[Markai6768]

My first thought was to agree with Comodave, but the bubbles bother me. I don’t think they are air bubbles but vacuum bubbles because the engine is pulling water out faster than the hose can supply it. The adapter does constrict what the hose can supply at least a little. My guess is that running for just a few minutes won’t be a problem but you might want to ask Seaboard Marine.

Seaboard Marine unfortunately wants $250/hour to answer simple technical questions.

Unless I am totally off base and interpreting their contact info incorrectly?

 

[firehoser75]

Seaboard Marine has a TON of free info available for someone who is OK with spending the time to have a good look around under "Tony's Tips".

Also, in the forums, forum members, Seaboard staff, and sometimes even Tony himself answer questions. It is free to join in, but like here you must "register" (username and password).

 

[Bacchus]

Seaboard Marine unfortunately wants $250/hour to answer simple technical questions.

Unless I am totally off base and interpreting their contact info incorrectly?

Does that apply to questions about their products?

 

[Comodave]

Does that apply to questions about their products?

I have bought a lot of parts from them and asked a lot of questions and never had any charge for the answers.

 

[LarryM]

+1 Very easy to deal with.

 

[Caballero II]

I am considering trying regular (every time I return to port) fresh water flushing, but I have a concern that I hope you might be able to help me address.

I have a fresh water garden hose connection to the top of the Groco Sea strainer assembly (from Seaboard Marine) for fresh water flushing that should work quite well.

https://www.sbmar.com/product/groco-arg-series-bronze-cap-with-freshwater-flush/

However, when I connect my fresh water supply hose to the bronze fresh water flush cap, at idle (Cat 3126 engine), and begin to close the through hull raw water supply I can see bubbles forming throughout the water canister of the Groco sea strainer.

This raises the following questions:



1). I worry that I might be supplying insufficient water supply to properly lubricate the Sherwood (engine driven) raw water pump? Is this concern reasonable when the Sherwood pump is being supplied at idle by an average garden hose water supply?

2). Since the fresh water garden hose supply volume is clearly less than the water supplied by an open through hull, am I at much risk of contributing to engine and wet exhaust component overheat IF I run the engine at idle for approximately 5 minutes?

3). When you fresh water flush, do you leave the through hull open and put up with a mix of sea water/fresh water, or do you close the through hull to achieve 100% fresh water supply?

Cheers...

Marcus

1. You can turn the hose up. We do about 1/2 volume. You just don't want to be so aggressive that you flood the engine, a theoretical possibility. We never have. Just check your outflow to make sure it looks healthy.

2. No. Theoretically you could provide too much water and flood the engine, but so far, we never have in out GB 36 with FL 120's. A simple observation would be to see if your outflow looked to be about normal.

3. We close the thru-hull before, or at the minimum during the fresh water flush. We are interested in keeping fresh water in all the lines.

 

[J.T kearney]

fresh water flush

Hi'
I use a product from Sea Flush that requires the original cap to be removed from the strainer. I remove the screen and insert a funnel type system with a 1 1/4 inch hose that I put in a 5 gallon bucket of fresh water. I weight the end the hose with a 1 1/4 inch shaft zinc to keep it on the bottom of the bucket. All this is being done with sea cock closed. I know 4 gallons will go through the system from winterizing with RV anti freeze. I keep the hose running in the full bucket. I don't know if this process would be considered a rinse but it does remove most if not all salt water. Its worked well over the years and saved on zincs.
I'm trying to find a pvc cap with the correct threading to build a hose connection that would allow me to connect a larger hose if needed.
Cheers
J.T.

 

[Mischief Managed]

A garden hose will definitely not keep up with the flow capacity of your raw water pump, but that's ok. The engine will be under no load and will not be making much heat, and as long as the impeller vanes in the water pump are wet, they won't suffer from water starvation.


I don't think you need 5 minutes of run time to flush. I feed my engine flush system from my on board water supply which has a flow meter. I aslo have engine start and stop buttons in my engine room and they are near the flushing valves and strainer through hulls.


My process: 1. I run 1 gallon of fresh water into the strainers with the through hull open and the engine off to push most of the salt water out of the strainer. 2. Without shutting off the flushing water, I start the engine while I simultaneously close the strainer through hull. 3 Once 3 gallons has flowed through the engine, I simultaneously shut the engine down and close the flushing valve. 4. I open the through hull so that everything is normalized for the next trip out.

 

[SteveK]

Would 5 gallons run thru engine be enough? My thought is to have a 5 gallon container to which the garden hose is also attached and let the engine suck from there with a bypass valve the amount of flow it wants. Observation will tell you if the garden hose can keep up.

 

[Nick F]

I guess I prefer to do this differently:

I do no like to shut the thru-hull as this could lead to subjecting the sea strainer to full freshwater hose pressure. It could also force water past the engine impeller pump and into the exhaust while the engine is not running.

My technique requires the hose flow to be greater than the engine flowrate.
I suggest this sequence:

1 (leave thru-hull open) connect FW hose and start FW flow (FW will flow backwards and out of strainer and thru-hull)

2 start engine and let it idle (FW will flow through engine with the excess continuing to back flow out of the inlet thru-hull)

3 Stop engine

4 Stop FW flow

 

[koliver]

I am considering trying regular (every time I return to port) fresh water flushing, but I have a concern that I hope you might be able to help me address.

I have a fresh water garden hose connection to the top of the Groco Sea strainer assembly (from Seaboard Marine) for fresh water flushing that should work quite well.

https://www.sbmar.com/product/groco-arg-series-bronze-cap-with-freshwater-flush/

However, when I connect my fresh water supply hose to the bronze fresh water flush cap, at idle (Cat 3126 engine), and begin to close the through hull raw water supply I can see bubbles forming throughout the water canister of the Groco sea strainer.

This raises the following questions:



1). I worry that I might be supplying insufficient water supply to properly lubricate the Sherwood (engine driven) raw water pump? Is this concern reasonable when the Sherwood pump is being supplied at idle by an average garden hose water supply?

2). Since the fresh water garden hose supply volume is clearly less than the water supplied by an open through hull, am I at much risk of contributing to engine and wet exhaust component overheat IF I run the engine at idle for approximately 5 minutes?

3). When you fresh water flush, do you leave the through hull open and put up with a mix of sea water/fresh water, or do you close the through hull to achieve 100% fresh water supply?

Cheers...

Marcus

I did an engine swap several years ago. Not being a mechanic, I had a senior Volvo guy do the initial startup. The boat was on the hard, so the thru hull water intakes were not supplying anything at all. I had no adapters. The mechanic simply removed the covers on the raw water strainers and inserted a garden hose. with nominal hose pressure, not enough to fill the bilge, the engines were started and run until he was satisfied with the installation. I doubt it was 15 minutes on each engine, but certainly longer than 5 minutes.

In your location, you won't be concerned with freezing if your water supply is full of salt water, but if full of fresh? What are you attempting to accomplish here? Will you follow the fresh water rinse with new salt water when you leave the boat in the winter?

 

[lwarden]

I'm a big believer in fresh water flushing and this year installed a better system to do it. I have a hose connection in the cockpit which goes to a 4-way tee by the engines. One line goes to each engine and one is teed into the AC coolant raw water intake. There is a low cracking pressure check valve on the line to the AC. Each input to the engines has a ball valve at the top of the sea strainer as does the AC connection.

For flushing I do the following:
1. Close all seacocks for the engines and AC raw water.
2. Turn on the hose (at this point it's running through the AC raw water line.
3. Start port engine, run for 2-3 minutes.
4. Shut down port and start starboard engine, run for 2-3 minutes.
5. Shut down port engine and turn off water supply.
6. Open all through hulls and shut off all ball valves leading to sea strainers.

Very important!: Check all through hulls are open as part of the routine checkout next time we use the boat.

This sounds like a lot of steps, but it's quick and only requires two trips to the engine room and prevents over pressurizing the water pumps or starving them.

 

[SteveK]

@lwarden
Why not leave thru hulls closed? I got lazy but used to shut all off until next time. I like to check over engines and fluids before a start of trip. Think I need to start process again to exercise thru hulls.

 

[lwarden]

Steve,
I did leave them open initially, and this is what the guys from SBMAR recommend, but I did a test and tasted the water in the aftercooler after flushing and it was till very salty. So, there was still a fair bit of salt water being sucked into the line since the hose can't keep up with the water pump flow. On a smaller engine with good hose pressure you would be fine, but my engines move a lot of raw water. I decided if I was going to flush them I wanted only fresh water in there.

 

[Slowmo]

I don't think some bubbles are likely to hurt the pump itself. As long as it has a reasonable flow of water the vanes are wet and lubricated. As to overheating that should not be an issue at idle and especially not in just a few minutes. I have used both the hose then the bucket of RV antifreeze, yes the engine draws at least as fast as the hose feeds it.

As to the 'quality' of the rinse, that's a different question. Diluting down the salt level will happen fairly quickly but there can be mineral deposits which are harder to remove. People sometimes use acids ranging from vinegar to hydrochoric acid or commercial flushes. For example the Starbrite marine descaling engine flush is 25% hydrocloric acid mixed with other substances (see MSDS). That helps remove deposits but some engine manufactures warn about potential seal damage. In addition you must make sure you rince out the flush full as it is very acidic.

 

[SteveK]

Steve,
I did leave them open initially, and this is what the guys from SBMAR recommend, but I did a test and tasted the water in the aftercooler after flushing and it was till very salty. So, there was still a fair bit of salt water being sucked into the line since the hose can't keep up with the water pump flow. On a smaller engine with good hose pressure you would be fine, but my engines move a lot of raw water. I decided if I was going to flush them I wanted only fresh water in there.

My question was since you had closed them, leave them closed until the next outing

 

[J.T kearney]

Fresh water rinse

Hi
On my boat I close my seacock valve even for an overnight stay on a mooring ball. I made a flying tag with sea cock closed printed on it and hang it on the ignition switch. I move it between the helm and sea cock valve. Trying to avoid another senior moment.
Cheers J.T.

 

[Caballero II]

Hi
On my boat I close my seacock valve even for an overnight stay on a mooring ball. I made a flying tag with sea cock closed printed on it and hang it on the ignition switch. I move it between the helm and sea cock valve. Trying to avoid another senior moment.
Cheers J.T.

Yes to this. I don't know why anyone wouldn't do this. The boat engine is fresh water flushed on return, or the next day on closing down until the next trip. Thru-hulls are all closed until our next trip, part of out check list is to open them on our pre-trip check list. I've also disconnected the fresh water hose while at the marina, and we just work out of our freshwater tank. 180 gallons from my fresh water tanks won't sink the boat. An open hose bib could.

I sleep better now. No open seacocks, no unlimited water entry.

 

[Marty4]

I installed a Tee fitting with a 3ft hose on the suction side of the strainer. Hose has a screw on cap on the end and I leave the hose in place.
To flush, I close the seacock, uncap the hose and stick it in a pail that is fed with a supply of fresh water from a garden hose. Fire up the engine and run at idle or at any RPM I want. As long as there is water in the pail there is no concerns with running with too little or too much water. The engine will suck what it needs based on RPM. When done with the flush screw the cap back on the hose, open the seacock and you are good to go.

 

[DennisB1]

I use the Groco fittings one for each cat 3208 engine. The fittings are below the waterline so I install the garden hose with a shutoff valve with seacock closed. When the hose is installed I open the seacock and start the engine the hose valve is opened then the seacock closed. I use 5 minutes run time then shutoff the freshwater supple then the engine within 5 to 10 seconds. There is still ample water in the line to line the impeller if you do it within a few seconds.
The bubbles you see are coming out of solution due to the pressure in the strainer being lower than the atmospheric pressure. The hose provides about 4 gallons a minute and the raw water pump would pump more with an open seacock. Still plenty of water to lube the impeller. Heating is not an issue at idle rpm engine in neutral. It’s inportant to shut the water off before engine shutdown to no overpressure the seals in the raw water pump.
I flush engine regularly.

 

[HopCar]

I installed a Tee fitting with a 3ft hose on the suction side of the strainer. Hose has a screw on cap on the end and I leave the hose in place.
To flush, I close the seacock, uncap the hose and stick it in a pail that is fed with a supply of fresh water from a garden hose. Fire up the engine and run at idle or at any RPM I want. As long as there is water in the pail there is no concerns with running with too little or too much water. The engine will suck what it needs based on RPM. When done with the flush screw the cap back on the hose, open the seacock and you are good to go.

I had a similar set up but instead of a cap on the hose I put a ball valve at the tee. My thinking was that I could also use the engine as an emergency bilge pump.

 

[Marty4]

I had a similar set up but instead of a cap on the hose I put a ball valve at the tee. My thinking was that I could also use the engine as an emergency bilge pump.

I can do the same by removing the cap, drop the hose in the bilge and close or throttle the seacock. My boat is only a small one (Ranger Tug R21EC) so quick and easy access to do this should the need arise. Good idea with the ball valve.

 

[kapnd]

100% City water will waste your zincs quickly, ans they don’t get anlong well with chlorine. Aluminum is recommended if your motor spends more time in fresh than salt water.
I have a deck fitting with a ball valve plumbed to the strainer for washdown, and I don’t close the seacock. No worries about flooding or over pressure or running dry.
It’s the first thing I do as soon as the boats tied up, I don’t even turn the motor off until it’s flushed, and then let the water hose run awhile to back flush the intake strainer and plumbing too.

 

[Lighthd]

Hi. Here is the link to Groco's instructions for their freshwater flush kit.
https://www.groco.net/media/file/file/s/s/ssc-series.pdf

I bought one last spring and haven't had the chance to install it yet. It's high on my to-do list for this spring.

 

[Taras]

I would definitely avoid "pressurized fresh water" as this can flood the engine. Why take that chance? All you need to do is connect the hose to your Fresh Water tank (at the tank and not after the fresh water pump). I had a fitting on my fresh water tank and just ran the hose to that so it was just "pulling" water out of my fresh water tank. I had bubbles too but that was not a big deal. Your impeller on your engine will pull a lot of water thru the hose and it will be plenty when you're at idle. If you have Twin Motors, do one engine at a time. I had 3306 Cat's and did this method for almost 7 years and it worked great. If you're worried about any temperatures on your motors, just shoot them with a temp gun to make yourself feel comfortable....Your temps should be fine.

 

[lwarden]

My question was since you had closed them, leave them closed until the next outing

Then I wouldn't sleep at night thinking I will forget to open them next time I use the boat. This way I have two chances to make sure they are open, once when I shut the boat down and next time I use it when I do my pre-flight check.

 

[J.T kearney]

Hi
Thats why I have a flying tag that says Seacock Closed and place it at the ignition switch when I have it closed and move it to the seacock when open. memory fades as years unfurl!!
Cheers J.T.
PS Nice Lindell