Engine flush

[Swank]

I am a believer of flushing raw water side of engines when boat will not be used for a long period of time.
I've read about the Groco flush system, and am leaning towards that.
Does anyone have a design of a homemade adapter that they would like to share.
Trying to save a buck when I can, so homemade would be a good option.
Thanks, Cheers!

 

[MV Moira]

There's a thread on this site at here where another member showed what he did.

On my previous boat I had the Groco sea strainers. I bought a spare top and had it drilled and tapped for a hose barb, then hooked up a 5 gallon bucket to it filled with antifreeze, closed the seacock, opened the valve on the bucket, and ran the engine for maybe 30 seconds to suck the antifreeze through the engine. For a larger engine you would need to make some changes.

 

[DDW]

I had sea strainer caps with flush fittings on the last boat, the new one doesn't have them so I'm about to make them. Drill and tap the lids for 3/4 NPT thread, a nipple, valve, and hose adapter. Using good quality components, the valve is $27 (Groco bronze), nipple is $9 (Groco bronze), hose adapter is $12 (McMaster brass - can't find a bronze one). So <$50. SBMar sells this arrangement for about $300. Does include the cap though so actually not unreasonable.

If your lids are plastic I would not do it. They need to be bronze, and thick enough to tap for 3/4 or 1/2 NPT. Alternative is a T in the line somewhere and a valve and hose adapter.

Flushing with a hose you have to be disciplined about the sequence so you don't apply full water main pressure to your raw water system.

 

[ancora]

I remove the hose from the bottom of the sea water strainer, start the engine, and pour in two gallons of CLR. Shut the engine, reinstall the hose, and let the engine sit for a few days. Start the engine and let it run until clear water comes out the exhaust.

 

[Taras]

Yes, I tapped into the lid of my groco strainers too. Just threaded in a valve with a handle, connected a fresh water line from the fresh water tank (do not use pressurized water- the engine must "pull" the water out of your fresh water tank with the impeller- just connect it to the water tank line "before" the fresh water pump). Then I would simply close the Sea Cock, then open the fresh water valve on top of the groco strainer and let the engine run for a few minutes until all salt water was flushed. Really simple process and saves a lot on maintenance over time. Inexpensive solution

 

[DDW]

You can use a hose. Just don't turn it on when the seacock is closed and the engine isn't running. The sequence is:

Open the seacock
Connect the fresh water hose, turn on the tap. Any excess pressure will vent to the ocean.
Start the engine
Close the seacock - engine will now suck from the hose
Let run for 5 or 10 minutes at idle
Shut the tap, immediately turn off the engine
Close the seacock

For normal tap pressure and a normal sized hose and even a smallish engine you won't be able to pressurize the raw water system - the engine will demand as much as the hose can deliver. Don't run over idle, the hose may not be able to supply enough to keep the engine cool.

 

[Swank]

Yes, I tapped into the lid of my groco strainers too. Just threaded in a valve with a handle, connected a fresh water line from the fresh water tank (do not use pressurized water- the engine must "pull" the water out of your fresh water tank with the impeller- just connect it to the water tank line "before" the fresh water pump). Then I would simply close the Sea Cock, then open the fresh water valve on top of the groco strainer and let the engine run for a few minutes until all salt water was flushed. Really simple process and saves a lot on maintenance over time. Inexpensive solution

That's exactly what I'd like to do.
Simple fix and easy to use.
I'd just fill a 5 gal bucket and monitor it to keep full for a few minutes.
Do you have a pic by any chance?

 

[luna]

My Groco ARG-3000 strainers are of a vintage that they came with bronze caps. Rather than drill and tap for 1/2" NPT (I felt the cap's thickness was too thin for those threads) I drilled and bored a hole 0.860" and installed a Groco TH500-W thru hull fitting and a bronze ball valve. Then a brass fitting to convert to a female hose bib and a brass hose bib plug. That was 18 years ago, zero maintenance other than a brush once a year with never seize.

Remove plug, twist on hose, provide the water, open valve and rinse the raw water circuit of your engine using whatever procedure that is safe. It takes about 8 minutes per side and that includes rinsing the gensets out.

 

[Taras]

 

[Swank]

Could a T with hose bibs be installed between strainer and pump.
Everything double clamped.
Close through hull, remove cap off of tee, push a hose onto protruding part of tee and place other end in a bucket?
When done, just cap off tee?
Would this work.

 

[Jerbro]

Could a T with hose bibs be installed between strainer and pump.
Everything double clamped.
Close through hull, remove cap off of tee, push a hose onto protruding part of tee and place other end in a bucket?
When done, just cap off tee?
Would this work.View attachment 169218

Like this?…..

 

[Taras]

Could a T with hose bibs be installed between strainer and pump.
Everything double clamped.
Close through hull, remove cap off of tee, push a hose onto protruding part of tee and place other end in a bucket?
When done, just cap off tee?
Would this work.View attachment 169218

Yes that could work but I would put the "T" before the strainer to protect the engine from sucking up anything unwanted. Also, I would probably put a valve in too. Lastly, you could also use this type of system as an "emergency bilge pump system". In case your primary bilge pump failed, you could use this as a back up "crash pump" (but again necessitating the "T" to be before the strainer).

 

[PhilPB]

This worked rather well for me. It was installed after the strainer.

 

[Jerbro]

Mine is also installed after the strainer as I trust the shore water supply to be clean. For the emergency bilge pump I have one of these at the pickup end on a shorter hose…

 

[lwarden]

I have the Groco bronze strainers and drilled and tapped it for a 3/4"NPT. It was a little on the thin side for my liking so I ended up silver soldering in the bronze nipple.
I have a single hose connection from the cockpit run to a 4-way tee fitting which goes to each engine and one to the AC raw water line just after the strainer. There is a check valve on the line to the AC. When flushing I close off all three thru hulls and open all three ball valves to the engines and AC and turn on the hose. With the engines off the water flows to the AC line. This prevents over pressurizing the main engine raw water pumps. I can casually flush each engine from the helm and then go turn the hose off, then go down to the engine room and open thru hulls and shut off all ball valves. The whole process takes about 5 minutes or so.

 

[ranger58sb]

I am a believer of flushing raw water side of engines when boat will not be used for a long period of time.
I've read about the Groco flush system, and am leaning towards that.
Does anyone have a design of a homemade adapter that they would like to share.
Trying to save a buck when I can, so homemade would be a good option.

Trac (the Barnacle Buster people) makes a replacement lid for Groco strainers, and they works well enough. We also have Groco SSCs permanently installed inline after our AC strainers; those too work fine.

We started with the SSCs and eventually also got some Trac lids for temporary use during flushing. I'm gradually finding that I think we have less temporary overflow with the Trac lids...

-Chris

 

[kapnd]

Tee between the strainer and pump, leave the seacock open, it will flush the strainer too after you turn the motor off.
An emergency bilge pump tee should definitely precede the strainer.

 

[smith6]

Be careful with this. I bought the plastic caps with hose fittings for my Groco strainers. However, the pressure from the dock hose turned out to be a bit too strong and caused my water pumps to leak as they were over pressureized. My suggestion and what i ended up doing instead was to remove the existing top of strainer and put a pipe a u shaped copper pipe that went up and over and into the strainer for more of a natural flow. water pumps don't like forced pressure. This setup worked great.

 

[DDW]

The water pumps were overpressurized while the engine was running? What size engine? What size hose?

I always have a valve at the end of the hose (there is one in the adapter cap also). Start the engine with the hose running and the seacock open. Then close the seacock. You can test the pressure by simply pinching the hose. Every time I have done this the hose pinches flat pretty easily, because the pump is sucking as much as the hose can supply at zero pressure. If not shut the hose valve down a bit to throttle it. I've never found that necessary.

If you pressurize your raw water system with static hose pressure, engine not running, seacock closed, yeah, that would be bad.

 

[smith6]

yes it happened while engine was running much to my surprise. 165 hp in line 6 volvo Penta

 

[rgano]

Many good ideas. I like to rinse my single Yanmar 315 HP engine EVERY time it is used. Being barn-kept, the previous owner showed me how he would have the boat placed on an outside "work" cradle for a couple of hours before it was placed back in its slot inside the boat barn so he could perform post-run maintenance including an engine (and generator if used) rinse. I inherited this main engine arrangement (and a similar one for the gen) which is installed after the sea strainer because there is no room to do so before the strainer. Also, the nice Groco type sea strainer cap would no work here because there is zero room over the stainer to attach a hose.

As to the need to close the sea cock while rinsing, I have this observation as a result of experience gained rinsing engines in my boat which lives in a covered lift behind the house. The shore water hose delivers sufficient water to allow the main engine to run at idle with the seawater pump sucking all it needs while a small amount of excess shore water backflows the sea strainers and exits the bottom of the boat. When I rinse the much smaller generator the water exiting the bottom of the boat is a pretty stout stream. Making a practice of shutting the sea cock for engine rinsing opens one to the accident of pumping water into a shutdown engine, forgetting to re-open it before next start, and possibly over pressurizing the water seal of the seawater pump.

I typically pull into my slip and catch the boat in its cradle but not lifted clear of the water with the engine left idling while I attach the shore water hose (with its own valved end connection shut) to the tee before opening the hose end valve and the tee's valve. Then I lift the boat clear of the water while confirming the exhaust water continues. After a few minutes, I shut the engine down as I shut the water supply valves.

I am certain that for most engines out there in trawlers that this procedure would work for wet slip kept boats with the assurance that you are not sucking any seawater in through the open seacock as long as shore water at normal shore water pressure is flowing into your system.

 

[DDW]

Maybe large hose and a lot of pressure? I can run my Volvo 70 hp 4 banger in the sailboat with a 75' hose on full, at idle it will almost suck the hose limp, easy to pinch it off with two fingers. Even on the 6kw NL genset which is a tiny engine and pump.

The question on leaving the seacock open is how do you know you aren't sucking seawater to mix with the fresh? You'd have to test the output to see I think.

 

[Comodave]

Be careful with this. I bought the plastic caps with hose fittings for my Groco strainers. However, the pressure from the dock hose turned out to be a bit too strong and caused my water pumps to leak as they were over pressureized. My suggestion and what i ended up doing instead was to remove the existing top of strainer and put a pipe a u shaped copper pipe that went up and over and into the strainer for more of a natural flow. water pumps don't like forced pressure. This setup worked great.

I have used the Trac adapters on engines before. But I use a 5 gallon bucket with a hose bib installed in the bottom side that I hook a short garden hose to. Then use gravity to run either the antifreeze or freshwater into the strainer. That way there is no water pressure other than gravity fed pressure.