Winterizing Mercruiser 4.5L 200HP

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Cortes100

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What is the blue wingnut plug just above the bottom front drain for? Shouldn't that be opened to drain any other water?

That bottom blue plug goes into the same compartment as the main drain (distribution housing).. The manual states if water does not come out of the main drain (that little spigot hose), you should pull this plug. Also states that in the video at the 1:30 mark. I've drained mine several times, and then pulled that bottom plug to see what happens. One drop may come out.
The upper blue plug is more of a vent to help the water flow better when the main valve is opened.
 
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QBhoy

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Haven?t seen one of these in the flesh, but if the drain system is similar to the previous MPI GM engines, as in the single point method....after opening the valve and vent and draining, I like to take off the quick connect hoses around the system anyway. Just to make sure.
 

Cortes100

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good day all.............so I have a little update since completing season 2 with the 4.5L.

Season 1, As noted above, I drained the engine of water and introduced Anti freeze via the blue vent plug on the upper left front of engine.

Season 2....I called several dealerships in Alberta, and confirmed with the Merc tech support. They all follow this procedure. Warm engine up to do oil changes, drain raw water using the single point system, then run on muffs to introduce the AF. Since the engine is dry, it will fill with the AF. Most important part is to drain the water before doing the AF.

I actually did that a couple times. Drain water, run on muffs with AF, drain AF, run on muffs with AF. Then drained the AF from the system, since the old rule is that "air does not freeze". I pulled every hose I could get at and they were all dry.
In all fairness, my last boat was a 2008. I did AF for the first few years, but the last 4 just drained via the single point system and left it empty. After 8 years, the inside of the manifold looked like new, so corrosion was not a factor.


Some might say, why not bring to dealer? Well every dealer in our area is a 2 hour drive away. That's a 4-5 hour trip and then back at a later date to retrieve the boat. Just not practical. The one dealer that is near here, has no idea what a 4.5L engine is, so figure I can figure this out myself.

And (no offense intended here), for all you people that comment, oh it's just like my XXX, or pull the hose and pour AF, single point can be removed, etc., if you haven't seen or worked on one of these 4.5L, then it's not fair for you to comment. The single point drain is an octopus of large hoses, not just a single fitting in the block or manifold. Things like the thermostat housing, large cooling hoses are on the back of the engine, not in simple view like the old 4.3 block.

As these engines get more popular, I'm sure we'll here more info on how to make service easier. But till then I hope this will help some of the DIY guys.
 

Pmalitsch

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Hi guys, I am new to the forum and this thread is exactly what I was looking for. Took it upon myself to winterize my MERCRUISER 4.5 MPI This year. My engine has the air pump mechanism to drain the engine. I followed all the typical procedures: warm it up on the fogging fuel, shut it down, drain the motor, then hook up the antifreeze tank and run through (took like 4-4.5 gallons before I shut it down and straight antifreeze was coming out the exhaust. Since it was drained it took like 30 seconds when I started it back up before anything came out- then a little bit of water then antifreeze. But, I forgot a small step but I don’t THINK it made a difference. Here is the video on how this works:

what I forgot to do, is remove the little blue plug-but this isn’t a typical water drain. It’s on the top side of the housing. I just went straight to the air pump - and a LOT of water came out both from the right front of r motor and back by the water pump. It took 5-10 minutes to drain. I called merc and I used -100 antifreeze. Based on what I told them they said I should be fine if there was any in there, but this plug appears to be like an anti-vacuum release or something. I also hooked the pump back up after flushing the antifreeze and with one pump straight antifreeze came out the bottom and I pulled the release real quick to stop it. Does anyone know if this step of removing the blue plug was 100% critical?
 
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