Cummins 330hp Fresh Water Flush

What is the best way to install a fresh water flush? I had one on my sailboat 54hp Yanmar. But then the raw water line was only 3/4". I was thinking of buying a spare Groco raw water strainer top cap and having a machine shop drill the cap and install a hose connection. Anybody have a better idea?

I put one of these on each engine ~ 9 months ago. Super easy install and easy to use. Can act as an emergency bilge pump as well.

Word of warning with fresh water flushing - do not turn on hose (if connected directly to flush valve) until motor is running. Doing so before motor is runinng can pressurise the raw water system and lead to water ingress problems.

Personally I use the 'bilge pump attachement' in a 20l bucket with a hose running in the bucket - so engine does all the pumping work and no risk of pressurising the motor.

Here's my set up. Works great and if you do it yourself - costs next to nothing. My engines are also Cummins 330B's.

My procedure: Connect city water to white hose ensuring red handle valve is closed. Start engine. Open red handle valve. Close sea cock. Observe water flow from engine. Run for 10 minutes. Stop engine and close red valve at the same time. Done

Don't let pressurized water into the strainer without the engine running.

Follow above procedure and all is OK.

Pgitug said:

What is the best way to install a fresh water flush? I had one on my sailboat 54hp Yanmar. But then the raw water line was only 3/4". I was thinking of buying a spare Groco raw water strainer top cap and having a machine shop drill the cap and install a hose connection. Anybody have a better idea?

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Pgitug and Timjet,

What a great idea. On the winter to do list for my Cummins 230.

Rob

timjet said:

Here's my set up. Works great and if you do it yourself - costs next to nothing. My engines are also Cummins 330B's.

My procedure: Connect city water to white hose ensuring red handle valve is closed. Start engine. Open red handle valve. Close sea cock. Observe water flow from engine. Run for 10 minutes. Stop engine and close red valve at the same time. Done

Don't let pressurized water into the strainer without the engine running.

Follow above procedure and all is OK.

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I like this set up for the cost and you do not have another joint in your cooling hose that can either restrict flow or cause a leak.

Timjet says:

"My procedure: Connect city water to white hose ensuring red handle valve is closed. Start engine. Open red handle valve. Close sea cock. Observe water flow from engine. Run for 10 minutes. Stop engine and close red valve at the same time. Done. Don't let pressurized water into the strainer without the engine running."

You don't need to close the sea cock in order to flush the raw water engine cooling system. If you turn on the fresh water and keep the sea cock open, the salt water will be flushed from the strainer and when you start the engine and run for 10 minutes, it will be all fresh water in the engine.

By keeping the sea cock open, you eliminate that potential problem of pressurizing the cooling system. Works really well in marinas with high water pressure. Have used this technique for over 35 years.

I"ve wondered if it's necessary to close the sea cock. I close it anyway because I leave the boat with all the sea cocks closed, except for the air cond.

Does the benefit of doing this outweigh any risks?

Closing sea cocks or installing a fresh water flush? What are the risks of either?

timjet said:

Closing sea cocks or installing a fresh water flush? What are the risks of either?

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Installing the flush and managing the process correctly re sea cocks.

We'll the risks are that you screw up the procedure and ruin an engine. The rewards are that your sea water circuit will remain cleaner especially the after cooler.

unless you have water lift mufflers or improperly designed exhaust I don't see any risk of running the water while the engine is not running.








My concern has always been that the city water flow is much less than the raw water pump flow and I wonder if it provides enough lubrication for those big impellers.


I would turn on the water before closing the seacock. closing the seacock would be necessary because so much more water comes from the outside that the fresh water would be diluted.

This is Groco's answer to the flush, emergency pump, winterize issue.
GROCO MARINE PRODUCTS
See their SSC, Safety Seacock Conversion.

Some hoses have upwards of 70psi. Strainer and sea water pump not designed to handle that. Might be ok, might not. Sea water pump effectively blocks flow if not turning. So with sea cock closed, no where for hose water to go and pressure will build.

Best to leave hose off unless engine is running. Start engine, open hose, run, turn off hose, stop engine.

Biggest risk is leaving boat with improper valve lineup after being done, then starting engine in that condition. I have fixed several engines damaged from this, and these were smart and thorough guys, not prone to screw ups. But it is easy to screw this up.

I flush mine if it is going to sit for any length of time. Just unscrew strainer lid and stick hose in. Close sea cock, start engine, turn on hose. Engine draws more than hose can provide, so it sucks some air, but this does not hurt anything. Hose off then engine off.

Fortunately one yard I like is on a fresh water river. Instant flush going up there!!

Otherwise in a normal year, boat runs every week at least. Five years of this and NO flushing and my coolers were in great shape for last springs cleaning.

I don't bother flushing with my duty cycle.

Pic shows my fresh water flush system

I put in the fresh water flush system shown in the attached pic. I drilled a hole near the edge of the cover to pick up some beef, tapped it for 1/2" NPT and added a street el, ball valve and a hose adapter. Cost for parts was about $20.

Since the raw water pump pulls more gpm at idle than my dock hose can supply, this is what I do: hook up the hose and turn it on, start the engine, close the seacock, run for 5 minutes, shut the water off and shut down the engine immediately, open the seacock. This procedure does not pressurize the raw water system and with the seacock shut avoids pulling seawater into the engine.

Since I installed and use it rigorously I have gone from 6 mo change out intervals for some zincs to two years. I even flush with the boat's fresh water supply now that I am on a mooring and don't have access to dock water.

David

Ski in NC said:

Biggest risk is leaving boat with improper valve lineup after being done, then starting engine in that condition. I have fixed several engines damaged from this, and these were smart and thorough guys, not prone to screw ups. But it is easy to screw this up.

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So true, but if it becomes a habit done everytime, less likely to happen.

Another issue to consider; make sure the hose you connect to the strainer can take the suction of the engine impeller. Note in my picture above the hose I use is a sanitation type hose, not likely to collapase. Most cheap garden hoses are not able to take the suction and may collapse.

Ski in NC said:

Some hoses have upwards of 70psi. Strainer and sea water pump not designed to handle that. Might be ok, might not. Sea water pump effectively blocks flow if not turning. So with sea cock closed, no where for hose water to go and pressure will build.

Best to leave hose off unless engine is running. Start engine, open hose, run, turn off hose, stop engine.

Biggest risk is leaving boat with improper valve lineup after being done, then starting engine in that condition. I have fixed several engines damaged from this, and these were smart and thorough guys, not prone to screw ups. But it is easy to screw this up.

I flush mine if it is going to sit for any length of time. Just unscrew strainer lid and stick hose in. Close sea cock, start engine, turn on hose. Engine draws more than hose can provide, so it sucks some air, but this does not hurt anything. Hose off then engine off.

Fortunately one yard I like is on a fresh water river. Instant flush going up there!!

Otherwise in a normal year, boat runs every week at least. Five years of this and NO flushing and my coolers were in great shape for last springs cleaning.

I don't bother flushing with my duty cycle.

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I'm confused about the "improper valve lineup".
How does that happen and how do you prevent it?
Can you elaborate?
Thanks!

Tunajoe said:

I'm confused about the "improper valve lineup".
How does that happen and how do you prevent it?
Can you elaborate?
Thanks!

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Someone leaves the seacock closed, or leaves the fresh water hose valve open. Then fails to open it when starting. Or capn or mechanic needs to start engines and does not know they are out of position.

"Valve lineup" is an industry term for a list of all valves and their positions for a certain operation.

I use a slightly different setup for raw water flush, consisting of a tee on the pump side of the strainer with a valve and hose adapter.
I always flush with the seacock open, never have to worry about overpressurizing, with the additional benefit of backflushing the strainer, intake hose and seacock.
This way you can turn on the hose, and take your time about starting the motor, with no worries about flooding it.
When a hose does appear to collapse, rest assured it is still passing whatever water is available to it from the faucet.
A five minute flush without full water supply is not going to damage your motor.

Ski in NC said:

Someone leaves the seacock closed, or leaves the fresh water hose valve open. Then fails to open it when starting. Or capn or mechanic needs to start engines and does not know they are out of position.

"Valve lineup" is an industry term for a list of all valves and their positions for a certain operation.

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Ski had a valid point. I generrally try to be at the boat when a mechanic is working on it. However 3 weeks ago I had a mechanic out to replace both impellers and he couldn't finish on the day he and I were there. He promised to come back in 3 days but I had to leave. So I discussed with him the position of all valves before he left the boat. Additionally I put sticky notes on the ignition key to remind him to open the valves before starting engines. I know this should be obvious but who wants to get into a pissing contest with a mechanic about who's at fault. When I do work on the boat that requires certain functions before engine start I put one of those tags with string attached and tie it to the ignition key with the reason written on the tag.

Bottom line; if you're not comfortable doing an engine flush - don't. Most folks don't do this and the engine is designed not to need a flush. Another advantage of flushing the engine is you excersize the sea cock, something most people probably don't do.

One question for Ski; if you leave the sea cock open will the fresh water entering the strainer from above prevent most of the salt water entering from the sea cock?

Depending on the engine and the garden hose flow, most larger engines will pump more than the garden hose can provide. So if you leave sea cock open, it will draw in a mix of fresh and sea water. That's why I close the sea cock and just stuff the hose in the open strainer. Then it pulls in a mix of fresh water and air, and no sea water. If system is sealed up aside from the fresh water hose, it will pull a partial vacuum on the strainer, but that won't hurt anything. And yes, if hose collapses, it is only collapsing partially, water is still flowing. It does not need much water to do a flush at idle.

Timjet,
I have never seen a manufacturers claim that their engines are designed to last in salt water without flushing, although they do not seem to encourage it either! (of course they want to sell you a new one as often as possible)
Bottom line is that if you run in salt water, you can add much to the reliability and longevity of your motor if you do flush it regularly.
It goes beyond the engine too, stern tubes come to mind, I have seen many shafts damaged from sitting too long in salt water, and dripless packing glands are particularly vulnerable.
Flushing becomes more critical the less the boat is used.

kapnd said:

Timjet,
Bottom line is that if you run in salt water, you can add much to the reliability and longevity of your motor if you do flush it regularly.
It goes beyond the engine too, stern tubes come to mind, I have seen many shafts damaged from sitting too long in salt water, and dripless packing glands are particularly vulnerable.
Flushing becomes more critical the less the boat is used.

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Agreed. It's why I flush mine. I'm willing to take the risk of screwing up the procedure.

Every time I'm at the boat and am not going to take it out I try and remember to turn the steering wheel stop to stop a couple of times. This flushes the stale saltwater out of the rudder packing glad and will prevent crevice corrosion. I had to replace a rudder shaft because of crevice corrosion.