Flush Raw Water System After Use

Greg_E

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I'm new to the inboard powered boats. I always had outboards.
I have twin 6.2L Mercruiser Horizons with closed cooling, 2003, and 2006, salt water use. I realize there are flushing ports on the engines but they are not convenient to use. I would like to be able to easily flush the raw water side of the cooling system. to extend the life of the heat exchanger, manifolds and fuel cooling system.
I have read on another forum(diesel engines) that some people have installed a T between the strainer and and raw water pump and and ran a hose above deck with a shutoff or cap where it can be easily connected a hose. I think I would use both the shutoff valve and cap as a belt and suspenders approach, just in case the the shutoff valve was inadvertently opened when using the boat. The fresh water hose on the dock can supply more water than the raw water pump uses at idle so it would back flush the strainer and no salt water should be drawn in.
Any downsides to doing this?
 

Bondo

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Any downsides to doing this?

Ayuh,...... So long as it's properly valved to control the water flow,.............. Nope, no down side,......
 

Greg_E

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Thank you for the reply. Can you explain what you mean by "properly valved"? The seacock for the strainer remains open so any excess fresh water would just flow out of the pickup. If you are referring to properly valving the flushing hose., yes I will do that.
 

achris

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On Horizon engines, the exhaust manifolds are in the closed cooling system side of it. The only things seawater touches are the raw water pump and the exhaust elbows...

Chris...
 

Scott Danforth

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The fresh water hose on the dock can supply more water than the raw water pump uses at idle

you may want to check this. the raw water pump will pump a significant amount (as much as 10gpm) and most hoses at a dock cant supply more than maybe 5gpm

you could simply install a super-flush unit, then the motor doesnt need to be running to flush.
 

Greg_E

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On Horizon engines, the exhaust manifolds are in the closed cooling system side of it. The only things seawater touches are the raw water pump and the exhaust elbows...

Chris...

I didn't know that. I still have a lot to learn about these engines. The raw water does cool the cool fuel modules, and they have been known to get clogged with salt.
 
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Greg_E

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you may want to check this. the raw water pump will pump a significant amount (as much as 10gpm) and most hoses at a dock cant supply more than maybe 5gpm

you could simply install a super-flush unit, then the motor doesnt need to be running to flush.

Before winterizing the engines I shut the seacock took the cap off of the strainer and put the hose into the strainer to flush the raw water system. The water was overflowing into the bilge unless I increased the RPMs, so I think I'm OK there. I will check out the super flush unit.
 

harringtondav

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I help my pal winterize the raw water side of his twin 350 cruisers. The strainers are reasonably accessible. He closes the sea ****, opens the strainer, starts the engine, and pours pink juice until I see a solid pink flow come from the exhaust. About 2 gal per engine.

An advantage of doing this is you have an annual opportunity to clean the strainer baskets. Salt isn't a problem on the Mississippi river. But sea weed, duck weed, and zebra mussels are a big problem. Same process for his A/C, generator and head.
 

Scott Danforth

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An advantage of doing this is you have an annual opportunity to clean the strainer baskets.

you will find in the manual that sea strainer baskets are supposed to be checked every time you fire up and cleaned frequently
 

Greg_E

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you could simply install a super-flush unit, then the motor doesnt need to be running to flush.

I did check out the Super-Flush system. The owners manual states that the engine has to be started within 15 seconds when using the flushing port on the engine or damage can be done to the engine. Does the Super-Flush system somehow
flush the entire system without running the risk of doing damage or is part of the raw water system not being flushed?

From the owners manual:
"Flushing the engine when it is not operating will result in water collecting in the exhaust system, damaging the engine. Do not supply flush water for more than 15 seconds without the engine operating."
If anyone can explain to me what exactly is happening in the exhaust system that water is collecting there, I would be interested in knowing.

Thanks to everyone that replied!
 

Scott Danforth

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they added the information to the manual because some bozo had his boat and truck on a fairly steep hill with the nose pointed downward and filled his motor up with water. I use the SF400 for years and never had a problem however I was never dumb enough to try it with the nose of the boat pointed down hill.

that bit of information was never in the first 5-6 years of the manual / instructions
 

Greg_E

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they added the information to the manual because some bozo had his boat and truck on a fairly steep hill with the nose pointed downward and filled his motor up with water. I use the SF400 for years and never had a problem however I was never dumb enough to try it with the nose of the boat pointed down hill.

that bit of information was never in the first 5-6 years of the manual / instructions

LMAO! If the nose of my boat is ever pointed down, I have worse problems!
 

muc

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they added the information to the manual because some bozo had his boat and truck on a fairly steep hill with the nose pointed downward and filled his motor up with water. I use the SF400 for years and never had a problem however I was never dumb enough to try it with the nose of the boat pointed down hill.

that bit of information was never in the first 5-6 years of the manual / instructions

I don’t agree with this. The boat would have to tilted soo far that the risers are now below the static water line. Don’t even think that’s possible.

That warning was added for boats with mufflers. Especially a type of muffler commonly called “water lift”, they are prone filling up with water when the engine isn’t running. And can cause water to back up into the cylinders.

If you have an I/O with Y pipe or straight thru transom exhaust, I wouldn’t worry.
 
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