Fresh water flush kit

Tacoma290 said:
I think the approach to flushing is tempered with how often you use the boat, how easy your flushing system is setup, and how closely you follow directions. @b_arrington is spot on with the merits of flushing. But you need to know that there are risks as well.

When I first bought the 340, I was happy that a Perko flushing kit had already been installed on it and the previous owner was emphatic that they flushed after every outing. I learned later that the reason for this was that the guy worked on an Alaskan crabbing boat, so he was away from the boat for long stretches of time.

So I learned to use the flush kit, which only allows a brief period of time between shutting the engines off after flushing, and shutting the water off. The design of our gas engines does not leave as margin for error as diesel engines seem to. One day, I took too long to shut the water off, and water filled part of the exhaust system, which resulting in a hydro locked engine. Through the solid advice of friends on this site and 'in the real world', I was able to clear everything out and avoided catastrophic damage to the engine. But after that panicked evening (and the cost of a new starter, new plugs, and bilge cleaner), I concluded that as long as I start the engines on a regular basis (usually once per week), that is better for me than risking that situation again. I live and work very close to the boat, so I am fortunate in the regard.

So, I don't use the flushing system with normal use. Since it is already installed, if I was gone for a month, I would use the flushing system prior to leaving. But I would be very quick about shutting the water off after the engines are off!

So the summary is that if you use the boat often, I would not consider a flush kit a must have. If the boat sits in the water for long periods, then the value of a flush system starts to increase. Good luck!
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This is interesting. I've thought about this as being a potential problem. I have a flush kit on the generator as well, and have on one occasion water went into the exhaust and oil. I ended up putting a valve post flush kit so I could shut down the generator and shut the valve at one time.

On the engines, I've found that the water pump seems to stop most of the flow when the engine shuts down, giving you time to shut the water offer. Have not had a backflow issue on the engines. Definitely need to watch out for it. I will say that I have talked to mercury about the mercruisers with the ECT exhausts (catalysts), and they strongly advised to flush after every outing.
 
b_arrington said:
I think the risk is related to what kit you have installed, and how you use it.

Mine is a bronze strainer-top water inlet with a valve. They way I do it, I never shut off my sea cock and therefore there is no risk of either water starvation nor of overpressurization. I hook up the water, start the engine, then open the fresh water valve. I flush, then stop the engine and let the fresh water run a bit longer. That backflushes the strainer as well.

I know someone that closed their seacock to flush and kept the water running when they shut off the engine. The water pressure cracked their plastic strainer body.

There's no harm in leaving the seacock open. Sea water is not going to get up into the engine while sitting at the dock. Fresh water is lighter, so it's not going to "fall out" and be replaced with seawater. Sure, there may be some mixing at while flushing but the dilution is minimal and better than leaving the seawater in the engine.
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Thanks for the follow up post Brad. Your system beautiful is in its simplicity. I would have no issue with using that system.

Unfortunately, my boat has Perko FlushPros installed. The instructions call for closing the sea cocks (and lacking the experience I have now, I followed them). More importantly, they have check valves built in to them that could still allow over pressurization even if the sea cock is open, which is why I am cautious in their use. The more I think about this, the more I think I would be better off just replacing these with a tee...
Just emphasizes the need to understand what is installed.
 
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Shaps said:
What strainers do you have?
I have GROCO strainers and use these
https://www.sbmar.com/product/groco-arg-series-bronze-cap-with-freshwater-flush/

edit:
and I too never close my seacock when flushing. All positive pressure goes out the bottom of the boat.
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That’s exactly what I have. One for the main, one for the gen set. Plus quick connectors sourced separately.

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Tacoma290 said:
Thanks for the follow up post Brad. Your system beautiful is in its simplicity. I would have no issue with using that system.

Unfortunately, my boat has Perko FlushPros installed. The instructions call for closing the sea cocks (and lacking the experience I have now, I followed them). More importantly, they have check valves built in to them that could still allow over pressurization even if the sea cock is open, which is why I am cautious in their use. The more I think about this, the more I think I would be better off just replacing these with a tee...
Just emphasizes the need to understand what is installed.
Click to expand...

I don’t like the FlushPros. The plastic makes me nervous.

Seaboard makes a bronze T flushing adapter. Might be too big for your hose though - fits 1.75 or 2” hoses.

https://www.sbmar.com/product/bronze-tee-adapter-for-freshwater-flush-system/
 
A little food for thought: waiting 4 years brings failure rate down to 25%. 45% at 5 years. At 3 years is 0.5%

last time I replaced my manifolds at 4 years and water had gotten inside. I have switched to every 3 years.
 
superwa said:
A little food for thought: waiting 4 years brings failure rate down to 25%. 45% at 5 years. At 3 years is 0.5%

last time I replaced my manifolds at 4 years and water had gotten inside. I have switched to every 3 years.
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People always wait on manifolds and risers to save some money. The irony is that when they fail the resulting damage is most often catastrophic, meaning the cost of repair dwarfs the cost of replacing the manifolds and risers in the first instance.

Manifolds every 3-4 yrs, impellers every 2, oil and filter annually. Why risk it, and you may catch something early before it results in catastrophic failure. Plus, it improves resale value.

If you can't afford the boat unless you scrimp on the maintenance, get a sailboat.
 
If anyone is concerned about over pressurizing the system, Hardin Marine sells pressure relief valves for that very problem and they are available in different pressure settings.

My last boat was a Bravo 1 7.4l and I added a flush manifold to it before the raw water pump. Also added the pressure relief with an overboard discharge. Switch manifold over to flushing mode, turn on tap water and it would dump overboard until engine started. Finish the flush, shut down engine and it dump overboard again until I shut off the tap water. Pretty simple and almost failsafe.
 
Bill Curtis said:
If anyone is concerned about over pressurizing the system, Hardin Marine sells pressure relief valves for that very problem and they are available in different pressure settings.

My last boat was a Bravo 1 7.4l and I added a flush manifold to it before the raw water pump. Also added the pressure relief with an overboard discharge. Switch manifold over to flushing mode, turn on tap water and it would dump overboard until engine started. Finish the flush, shut down engine and it dump overboard again until I shut off the tap water. Pretty simple and almost failsafe.
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Seems unnecessary, when the engine is off the water dumps out of the drive.
 
scoflaw said:
Seems unnecessary, when the engine is off the water dumps out of the drive.
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Not if the manifold closes off the raw water intake before the raw water pump. I did it that way so there would be no possibility of salt mixing with fresh and I could winterize without wasting pink stuff out the drive. Plus there is a raw water shutoff (like a sea cock) incase of a part failure and taking on water. If I want to backflush the drive, just open that valve with tap water on, after engine shut down.
 
I installed full flow Tee's and ball valve's (1.25" ID) in my raw water intakes between the seacock and strainers. For quick connects I used male and female Banjo fittings along with a 3' section of reinforced water hose (with a strainer at the end).
I close the salt water side of the sea cock and open the ball valve on the tee, the end of the flushing hose sits in a 13 gallon square bucket (fits perfectly in the bilge) and it has a solution of fresh water and Salt Away.
I flush at idle for maybe 5mins and then run up to 2,000rpm until the bucket is just about empty and then slowly bring it down to idle and shut down. I then close the ball valve.
I know I have introduced fresh water/Salt Away completely thru the engine as you see the suds in the exhaust.
I have "cleared the baffles" in the manifold by running it up to 2,000rpm before shutdown.
The Salt Away solution now sits in the entire raw water side (including the strainer).
When I open the seawater seacocks and start the engine to go out, no rust comes out with the exhaust so that is something good in my book.

Since I always think ahead.....when the flush hose is attached to the Tee, it can always be used as an emergency bilge pump by running the engine and opening the ball valve.....the strainer at the end keeps debris out and in a really bad flooding event you would be surprised how much water that little seawater pump moves!
 
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