Proper use of Mercruiser fresh water flush kit wanted

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amajamar

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I have twin Horizon 5.7's FWC Ser#OL677287 with factory fresh water flush kits installed. My first thought was that obviously you close the seacock and hook up the hose and run the engines for a while and flush out the manifolds and risers. However, I rebuilt the raw water pumps this weekend and I notice that the flush kit is installed in the line AFTER the pump on it's way to the oil cooler. So that lead me to wonder what happens to the pump impellor as it is spinning with no fresh water coming to it, as the fresh water is injected just after it. Will the pump impellers be damaged?

Just wondering about this, as it would seem that the fresh water flush would be cut into the line BEFORE the pump.

In any event, what is the correct procedure to use the factory fresh water flush kits?

Thanks in advance!
 

Fun Times

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Re: Proper use of Mercruiser fresh water flush kit wanted

Hi there, any chance you can post a few photos of your flush kit? Would kind of like to see where it's at if possible.

Also does your big hose between the thermostat housing and circulating water pump have the drain system on it that looks like part # 861590A05 in the link below? If so, then I believe you could have used Mercruiser engine flush connector kit 22-861932A1 to flush without running the engine. http://outboardparts1.com/merc/13AG21/171.pdf
Or item #'s 5 & 13, http://www.mercruiserparts.com/bam/subassembly/31841/11741/180

Since this engine model has closed cooling (factory installed fresh water), as a guide, here is the proper list for this exact engine,,https://www.perfprotech.com/mercury...cooling-system/assembly/4835/160?umodel=22854
model,

Here is this engine models complete parts catalog for you. https://www.perfprotech.com/mercury-marine-parts-catalog/umodel/22854

The way you describe your flush kit, you cannot run the engine or your rubber impeller will go bad in no time at all.
 
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amajamar

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Re: Proper use of Mercruiser fresh water flush kit wanted

I can't post any pictures today, but yes my kit is the one shown on your first link. The tee is installed at the top outlet of the pump, so effectively after it. I have a fresh water cooled engine so I'm not sure that the second link applies to me. The description of the flush kit in the first link says "flush with engine running", so I would be interested in how Mercruiser describes it's use.
 

Fun Times

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Re: Proper use of Mercruiser fresh water flush kit wanted

The kit may look more like this installed. Item's 9-16 are some of the kit. If you have this kit, you need item #10 to run the engine.
http://www.miamimarina.com/frontend...A4A5D722FED86A2?image=blocks/COMMON/34316.gif

Miami Marine Specialists,Mercruiser,Mercury,Yanmar,OMC,Volvo Penta,Suzuki

Be sure to see the last post.
mercruiser flush system

If your kit is connected wrong like your saying, you can't run the engine. If the kit is inline with the transom water pick up hoes, then you need to run the engine.

If you had the big hose between the circulating and thermostat housing then you use the fitting part number 22-861932A1 and don't run the engine.
 

amajamar

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Re: Proper use of Mercruiser fresh water flush kit wanted

After reviewing the parts breakdown on the link you provided, and at the Merc website, I am noticing a major conflict. From those images it looks like the tee is fitted to the lower port on the raw water pump, which would make sense from the flush kit perspective, but hose 27, which shares the tee with the flush kit, is the transmission oil cooler supply hose. Since the supply water must flow through the oil cooler, it seems that Merc designed the flush to be after the pump, which is certainly very confusing.

Is there any diagram which shows the proper water flow through the pump body on this engine? I am pretty certain that the lower port is raw water intake and the upper port is out to cooling system, as both engines were set up that way.

Do you know where the installation and usage manual is for the fresh water flush kit is located? If so, it may give some answers.

Fun Times, do you see it the way I am seeing it, or I missing something obvious???
 

amajamar

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Re: Proper use of Mercruiser fresh water flush kit wanted

I located the Mercruiser manual which explains how the flush kits are supposed to be used and now I understand why they are installed after the pump. They are designed to be used with the engine off, and the blue drain plugs removed from the bottom of the manifolds. A 10 minute flush like that, and then a 15 second flush with the plugs replaced in order to clear the risers and elbows.

That said, I have relocated the flush kits to the fitting before the pump, so that I can flush with the engine running and the seacock closed. Would this create any issue? Will I damage the impeller running the hose pressure into the pump while the engine is running? Should I regulate the water flow in any way or can I just use the hose pressure as is? This seems like a much more logical way to flush the engines without filling the bilge with sea water (the Merc book does recommend running the bilge pump during the flushing operation!).
 

Fun Times

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Re: Proper use of Mercruiser fresh water flush kit wanted

I located the Mercruiser manual which explains how the flush kits are supposed to be used and now I understand why they are installed after the pump. They are designed to be used with the engine off, and the blue drain plugs removed from the bottom of the manifolds. A 10 minute flush like that, and then a 15 second flush with the plugs replaced in order to clear the risers and elbows.
Thanks for the note, I've never read that in the past.:cool:

That said, I have relocated the flush kits to the fitting before the pump, so that I can flush with the engine running and the seacock closed. Would this create any issue? Will I damage the impeller running the hose pressure into the pump while the engine is running? Should I regulate the water flow in any way or can I just use the hose pressure as is? This seems like a much more logical way to flush the engines without filling the bilge with sea water (the Merc book does recommend running the bilge pump during the flushing operation!).
I would say it depends on how strong your city water pressure is at the water spigot. If it's really strong then half to 3/4 open, if it's weak, then you need full open. The manual says to run it at idle speed and don't go over 1200 RPM. Flush for 5-10 minuets. Be sure the thermostat is open. At idle speed engine cold, it takes on average 8 minuets to fully open.;)

Since you don't have a bravo drive and you do have a seacock valve, you'll want to close it first before starting. That said it never hurts to back flush the inlet hose and fitting for a bit especially if the boats still sitting in the water.

If you had a bravo drive, they want you to flush the drive and engine at the same time. Turn water on flush the drive then start engine.
 

Scott Danforth

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Re: Proper use of Mercruiser fresh water flush kit wanted

it will create an issue if you forget to open the seacock and attempt to go boating.
 

amajamar

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Re: Proper use of Mercruiser fresh water flush kit wanted

Thanks for the note, I've never read that in the past.:cool:

I would say it depends on how strong your city water pressure is at the water spigot. If it's really strong then half to 3/4 open, if it's weak, then you need full open. The manual says to run it at idle speed and don't go over 1200 RPM. Flush for 5-10 minuets. Be sure the thermostat is open. At idle speed engine cold, it takes on average 8 minuets to fully open.;)

Since you don't have a bravo drive and you do have a seacock valve, you'll want to close it first before starting. That said it never hurts to back flush the inlet hose and fitting for a bit especially if the boats still sitting in the water.

If you had a bravo drive, they want you to flush the drive and engine at the same time. Turn water on flush the drive then start engine.

Regarding the thermostat being open, my engines are FWC, so probably less important about that as I am only flushing the raw water system and manifolds and risers, correct?
 

Scott Danforth

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Re: Proper use of Mercruiser fresh water flush kit wanted

that is correct.

since your engines are FWC, why worry about running the engine to just flush the manifold and risers. I would leave the flush kit after the raw water pump in that case, and keep your life simple.

the raw water pump doesnt care if it gets flushed or not.
 

amajamar

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Re: Proper use of Mercruiser fresh water flush kit wanted

that is correct.

since your engines are FWC, why worry about running the engine to just flush the manifold and risers. I would leave the flush kit after the raw water pump in that case, and keep your life simple.

the raw water pump doesnt care if it gets flushed or not.

That is a really good point, but the blue manifold plugs are really difficult to access on a regular basis on my boat. Not to mention constantly dumping gallons and gallons of water into the engine compartment is not something I really want to do. I think this is a good compromise for me. I just wanted to make sure that I wouldn't hurt the impeller by putting water pressure behind it.
 

Scott Danforth

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Re: Proper use of Mercruiser fresh water flush kit wanted

so leave the plugs in for 90% of your flushes.

start the flush, grab a can of liquid refreshment, after 15 minutes or your second can of refreshment, turn the water off and disconnect the hose. removing the blue plugs is just to shorten the flush cycle and ensure that any sediment has been removed.

if your in fresh water, no need to even flush. if your in salt water, flushing extends the life of your manifolds and risers from 3-5 years to about 6-10 years
 

amajamar

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Re: Proper use of Mercruiser fresh water flush kit wanted

so leave the plugs in for 90% of your flushes.

start the flush, grab a can of liquid refreshment, after 15 minutes or your second can of refreshment, turn the water off and disconnect the hose. removing the blue plugs is just to shorten the flush cycle and ensure that any sediment has been removed.

if your in fresh water, no need to even flush. if your in salt water, flushing extends the life of your manifolds and risers from 3-5 years to about 6-10 years

I am in salt water and that's why I plan on flushing. Regarding flushing with plugs in, that would be dangerous for my engines as I have inboards and that could potentially fill the mufflers up enough to send water back towards the engines. Either way, the liquid refreshments are included in the procedure...! :cool:
 

Scott Danforth

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Re: Proper use of Mercruiser fresh water flush kit wanted

good point on the mufflers and the static water line. then in that case, re-plumb and run the motors. I wouldnt bother pulling the blue plugs for 90% of the flushes, probably just 3 or 4 times a year to flush out sediment.
 
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