Fresh water flush system

JoeWhite · Mar 2, 2016

I am not sure what you are referring to when you say "flush system". There is the raw water system and there is the fresh cooling water system. You can flush the fresh water cooling system. It contains the antifreeze. This water circuit may run through the hot water tank - if yours is equipped with one. You need to flush this periodically - I am not sure how often, may be 5 years. You drain the coolant that has antifreeze in it. I am not sure where the drain plug is - usually on the lower side of the engine. This is a good time to replace the water hoses. Then fill with distilled water and run the engine. Drain again then fill with 50/50 water and antifreeze. You may need to burp the circuit - as in removing all the air that may be trapped in the engine. Take the old antifreeze to a recycling center.
There is no flushing for the raw water circuit. You may clean the dirt in the filter.

dhays · Mar 12, 2016

Oldish thread but....

Some boats are setup with a fresh water flush system where there is a hose connection to the raw water system before the sea strainer. The idea is that you connect a fresh water hose to the hose connection, turn on the fresh water and close the raw water seacock and run the engine. This flushes the salt water out of the heat exchanger. Run the engine for 10 minutes.

I don't know the actual procedure and it likely varies with how the boat is setup.

Stu Jackson · Mar 12, 2016

Gentlemen, you are perhaps misunderstanding how to flush (and/or winterize) a FRESHWATER cooled engine.

NEVER connect a hose directly to the raw water pump and system.

Never.

Winterizing an Engine on the Hard (Thanks to Maine Sail) - NEVER connect a hose to your raw water pump inlet - NEVER!!!

http://forums.catalina.sailboatowners.com/showthread.php?p=873073&highlight=winterizing

dhays · Mar 13, 2016

Hi Stu,

I don't believe he was referring to winterizing a boat since he is in Florida however my assumptions are notoriously wrong. He also didn't mention that his boat was on the hard (maybe it is?). There are some boats that are setup to do a freshwater flush of their raw water system, much like outboards are flushed. The benefits of this are that you then have fresh water, not salt or brackish water, sitting in the heat exchanger. Not common on sailboats and I don't think Catalina ever did this.

BTW, your point about not connecting a hose with pressurized water is a good one. I don't have a system to fresh water flush my raw water system.

woodster · Mar 13, 2016

that connection in the cockpit sounds more like a fresh water supply the the plumbing system for sink,shower,and head sink water ...trace the line and see where it goes ...it may be tied the the fresh water supply instead of the engine ..make double sure ...a pick would help for sure

Maine Sail · Mar 13, 2016

Guys,

As Stu mentioned NEVER EVER, EVER connect a garden hose directly to your vessels raw water system. You can destroy your engine at the worst, and hydrolock it in the least.

The Raw water pump is designed to pump water in-concert with engine RPM at a designed flow rate. The garden hose will pump water faster than the boat can eject it from the exhaust and when the exhaust gets full it sucks water into a cylinder. Next the piston tries to compress that water....D'oh.... Bye, bye connecting rod, crank etc....

Beyond that there is no need to fresh water flush the raw water system on these boats. They are designed to handle salt water for years and years and years... Change and/or flush teh coolant every 1-3 years and beyond that don't over-think the raw water side...

Skipper · Mar 13, 2016

I agree that it's likely a winterization connection. Mine has this, but it's in the engine bay, and merely a T fitting with a brass screw cap. Don't use it anymore, because I left the freezer for SoCal. :-D

Connect a garden hose to the fitting, and drop the other end into a bucket containing your non-tox antifreeze. Close the raw water seacock, and on your boat any other valves required, and start the motor. When bucket is near empty, shut motor and stow your gear. Done. Leave seacock closed.
This can be done on the hard or water.

There are more winterization needs and details IE quantity and type of antifreeze, other boat systems, and some etceteras, but you probably won't need it anyway and that's a separate thread.

Might be in Florida, but parts of Florida can freeze too. Also the boat may have originated elsewhere.

Skipper · Mar 13, 2016

Skipper said:
I agree that it's likely a winterization connection. Mine has this, but it's in the engine bay, and merely a T fitting with a brass screw cap. Don't use it anymore, because I left the freezer for SoCal. :-D

Connect a garden hose to the fitting, and drop the other end into a bucket containing your non-tox antifreeze. Close the raw water seacock, and on your boat any other valves required, and start the motor. When bucket is near empty, shut motor and stow your gear. Done. Leave seacock closed.
This can be done on the hard or water.

There are more winterization needs and details IE quantity and type of antifreeze, other boat systems, and some etceteras, but you probably won't need it anyway and that's a separate thread.

Might be in Florida, but parts of Florida can freeze too. Also the boat may have originated elsewhere.

Just thought of something. The location of the spigot is illogical for a direct connection to the raw water circuit. Too risky for error.

It might be a raw water washdown. With a separate connection to the strainer.
Especially in Florida, where many people are sailors, but everyone is a fisherman.
Look for a pump inline. Is there a washdown pump breaker on the panel?

Skipper · Mar 14, 2016

marathonguy said:
Thanks for all the responses. I think dhays was correct. I believe this is a fresh water flush of my raw water system. This is not a winterazation issue and the boat is not on the hard. I think it is similar to how outboard's are flushed of salt water. The system is connected to my raw water system. I did trace the water to raw water strainer. But I don't want to run pressurized water through the system. Kinda why I asked the question. I think I am just going to forget about trying to use this fresh water flush. Again thanks for the responses.

It might be used for flushing, but not in the same fashion as an outboard.
You would let the engine draw from a bucket, same as winterization method.
BTW, on the hard or on the water, people winterize their motors.