Mercruiser Winterizing Question #1,378,456

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ChrisCraftJohnny

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Simple question:

If you back-fill all the exaust manifolds with Anti-Freeze,
Do you run the risk of filling up a cylinder with A/F that might have the exaust valve open?

Or is there a flapper of some sort that prevents this. I have yet to take apart a marine engine yet, so I am not sure.
 
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BeaufortTJustice

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Re: Winterizing Question #1,378,456

Re: Winterizing Question #1,378,456

My understanding is that the part of the exhaust manifold that actually carries the exhaust gases out are separate from the cooling passages that run through them. I would not recommend putting antifreeze into the "exhaust" passages of the manifold, just the cooling passages.

There usually is a flapper, but it is probably further down the system and is designed to prevent water from being pushed up into the exhaust from backing down or reversing.
 
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ChrisCraftJohnny

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Re: Mercruiser Winterizing Question #1,378,456

Yes, I understand that.
But from what I have read, the exaust gas and water mix together and exit the boat via the transom plate holes and the prop. It might mix together further down the line after the flappers?

Anyone know? Don S. maybe?

Johnny
 
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a70eliminator

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Re: Mercruiser Winterizing Question #1,378,456

ChrisCraftJohnny said:
Simple question:

If you back-fill all the exaust manifolds with Anti-Freeze,
Do you run the risk of filling up a cylinder with A/F that might have the exaust valve open?

Or is there a flapper of some sort that prevents this. I have yet to take apart a marine engine yet, so I am not sure.
Click to expand...
It sure could happen if you used an external pump and plugged off the outlet at the drive, the exhaust and water do mix at the outlet of the manifold therefore it is possible to back into a cylinder through an open exhaust valve if circumstances were right.
 
bigskiohio

bigskiohio

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Re: Mercruiser Winterizing Question #1,378,456

it mixes past the riser elbow but if you have a bad gasket at the riser it would leak in.
 
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a70eliminator

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Re: Mercruiser Winterizing Question #1,378,456

Reguardless where they mix before after within, they still mix, why do you think exhaust flappers are there for, key words here are backfill manifolds and is a dangerous move if you ask me.
 
RoyR

RoyR

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Re: Mercruiser Winterizing Question #1,378,456

I think the risk out way the reward....don't do it!
 
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dubs283

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Re: Mercruiser Winterizing Question #1,378,456

why would you back fill your exhaust manifolds with anti-freeze?

just drain them and be satisfied in knowing that air does not freeze
 
Lou C

Lou C

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Re: Mercruiser Winterizing Question #1,378,456

If you are just filling the mainfold with AF through the hose from the thermo housing till it runs out the exhaust there is no way the AF can get into the exhaust gas passage unless there is a leak in the manifold itself (ex passage near the head) or the gasked between the riser and manifold is leaking (possible but then you'd have a water leak when running anyway). OMC in their manual lists doing this as part of the optional winterization procedure and I've done it every year and never had a problem.....
 
Bondo

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Re: Mercruiser Winterizing Question #1,378,456

Ayuh,... The water mixes at the aft of the riser elbows, as noted by bigskiohio,....
It's After the exhaust has risen,+ is falling,...
Water from the manifolds/ hoses can't climb the hill,... No fear there...
 
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maddog2112

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Re: Mercruiser Winterizing Question #1,378,456

Wow, now I know why some of you guys say, just pull all the drain plugs cause air don`t freeze. This a/f backfill creates many questions. Am I wrong here in thinking , if you drain all the water from plugs, (which theoretically would be enough)reinsert plugs, and even if you just poured 3 or 4 gallons of a/f into the 2 exhaust manifold hoses at the thermo housing of a 4.3 or 5.0 merc, wouldn`t it all end up in the block via the exhaust manifolds?
 
Bondo

Bondo

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Re: Mercruiser Winterizing Question #1,378,456

and even if you just poured 3 or 4 gallons of a/f into the 2 exhaust manifold hoses at the thermo housing of a 4.3 or 5.0 merc, wouldn`t it all end up in the block via the exhaust manifolds?
Click to expand...

Nope,... As explained,... It'll end up on the ground...
 
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maddog2112

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Re: Mercruiser Winterizing Question #1,378,456

Ok, what about filling thru the large hose coming off the water pump. I did that too and the a/f had to go somewhere. It didn`t spill on the ground, I assume it would have to end up in the block.
 
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ChrisCraftJohnny

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Re: Mercruiser Winterizing Question #1,378,456

Thanks again Bond-O!

Also, what I mean by "back-fill" is:

When you pour A/F down the water outlet/themostat housing and it's hoses, you are "back-filling" the cooling system. The way I read the flow chart from my Merc manual the cooling water flows from the outdrive up into the engines water pump, through the block, into the thermostat housing,
(where the temp rises until OT, Stat. opens) then flows to the bottom side of the exaust manifold then overboard.

Also, I believe water flows to the exaust riser at all times for mixing with the exaust gases. The bottom side of the exaust manifold is T-stat controled so the engine is allowed to reach operating temp.

With that being said, if you pour A/F down the themostat housing and it's related hoses you are "back-filling" the system.

Johnny
 
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