350 MAG winterizing - which method is correct?

[saaristo]

I have a 2005 raw water cooled 350MAG in my boat and I was wondering which of the two methods is correct (both found from youtube)
1. Drain all the water from block and manifolds/risers, leave the blue plugs off, then disconnect the big tube from the circulation pump and t-stat housing, flip it around, attach it on t-stat housing upside down and use it as funnel when dumping antifreeze into this tube. When the antifreeze starts pouring out from the blue plugs holes youre done.
2. Drain water from the engine by removing blue plugs, then reattach the blue plugs again. Then disconnect the big tube from t-stat housing and pour antifreeze into this tube until it comes out from the same t-stat housing opening where the tube was attached. Also disconnect the risers tubes from t-stat and pur antifreeze into these tubes until it comes out from the exhaust.

Now maybe I am overthinking this whole thing and my mind plays tricks on me regarding t-stat function, but which of these methods would really put the antifreeze through whole block?

 

[Lou C]

#2, just make sure to use antifreeze that will stay liquid down to the coldest temp you would expect. #1 is just a waste of antifreeze, if you're not leaving it in, don't bother to use it. Remember you DRAIN to prevent FREEZE damage, AF is ONLY for corrosion protection.
Also, there may be a PS cooler and/or fuel cooler in line with your raw water intake hose, you need to find out if those have drain plugs that need to be removed also.

 

[Bondo]

Ayuh,...... As long as you start with the entire raw water system, Drained,.....

You can do whatever ya want with the antifreeze,.....

Air, don't freeze,....

 

[saaristo]

Thank you guys for reply. My only I/O experience so far is with a newer VP that was half closed system, so way safer in regards of potential freeze damage.
This one is a bit different animal. Seems there are no block nor manifold drains at all but just one blue plug on the t-stat housing and one on the grey ball-like round tubing piece on the front bottom of the engine. Suspicious of draining everything through just one bottom drain opening. In addition was thinking I will detatch the water intake tube from the impeller housing as well when draining

 

[tpenfield]

Think less about the procedure and more about what you are actually doing to the engine

#1 is more of draining with a splash of antifreeze. most of the AF will drain out fairly quickly and not really get anywhere in the engine.

#2 is a drain and fill.

#3 (there is always a #3 ) could be #2 and then drain everything via the blue plugs.

Either way can be fine as long as you are protecting the engine from freeze damage. When you leave AF in the engine, you want to be sure to use a strong enough AF. The -50 is not strong enough for some regions that get well below 0F in the winter.

 

[saaristo]

Probably going for # 3, just to be sure that there is no raw water anywhere and have some sort of rust inhibotors on inner walls of the water jacket.
Did some prepwork today and discovered some features I haven't seen on my previous VP-s.
Under manifold there is no drain plug but there is some sort of "device", pointed with red arrow, looks like a valve or something, should I detach the hose clamp and poke it with ziptie when draining?


Same thing with the block, no drain but hose that runs to drain point. Again to be sure the water drains I thought removing the hose and poke it with wire but whats that in the red circle, some sort of quick release lever? Didn't dare to poke it too much.

 

[Lou C]

That looks like some kind of single point drain system…follow the hoses & see where they terminate. Is there a valve or cap on the end?
If so the one thing that you want to watch for is how much water actually drains from each one. The block should hold 2 1/2–31/2 gallons each manifold about 1/2 gallon. When I fill my 4.3 V6 with AF it usually takes about 4 gallons to fill the whole thing; a V8 might be closer to 5 gallons.
If they don’t drain then you have to pull the hoses & rod out the drains….

 

[Bondo]

Probably going for # 3, just to be sure that there is no raw water anywhere and have some sort of rust inhibotors on inner walls of the water jacket.
Did some prepwork today and discovered some features I haven't seen on my previous VP-s.
Under manifold there is no drain plug but there is some sort of "device", pointed with red arrow, looks like a valve or something, should I detach the hose clamp and poke it with ziptie when draining?
View attachment 371749

Same thing with the block, no drain but hose that runs to drain point. Again to be sure the water drains I thought removing the hose and poke it with wire but whats that in the red circle, some sort of quick release lever? Didn't dare to poke it too much.
View attachment 371750

Ayuh,..... That appears to be one of Merc's frozen block guarantied systems,....
Under the manifold, loosen the hose clamp, 'n pull that hose off to drain it,.....
On the block, the white plastic clip pulls out to release the hose,.....
Then poke, 'n prod the hole to clear any debris,....

 

[Lou C]

These systems might work on an aluminum block engine but on cast iron it’s risky because of how cast iron corrodes; it flakes off and those flakes clog up those single drain systems. Maybe in fresh water that’s not corrosive but in salt…risky.
Going to winterize my brothers boat with the Merc 4.5 V6, that has that single point system. Last year it worked fine, we’ll see what happens this year! I might leave the plug in when draining it; then put a 5 gallon bucket under the garboard drain and see how much came out.

 

[Scott Danforth]

The small lines at the bottom of the block run to a manafold.

Pull the lines at the bottom of the block and poke the fittings to make sure they drain

Then remove the hose and clean out the debris

Those bottom lines plug up and your block cracks. It's supposed to be a "single point drain" but it's a guaranteed broken block because the system does not work after the first year or two.

 

[Lou C]

Yep that's what worries me. I'll use the 5 gallon bucket under the garboard drain, if it comes close to filling it, fine, if not then I hope we can reach the drains on the block on this boat. Merc really should have alternate instructions on what to do if the damn thing clogs up!
The old style boats are a pain too because you have to move the seats out of the way to get to the drains but at least you know for SURE it is DRAINED!
I think Merc made the fittings on the block bigger when they started building their "own" version of GM's old 4.3. Which is I guess just slightly modified with a modern integraded fuel and igition system that works great but would cost a King's Ransom to repair if it ever breaks.
As for me I'll take manual drains, a points distributor and a well tuned Quadrajet, anyday!

 

[saaristo]

Tried to loose those block drain hoses today, but no luck. I'm afraid I'll break something. Should the gray clip be pushed towards block or pulled perpendicular to the hose/fitting?

 

[Bt Doctur]

push the tab inward and twist, then probe with a nail to insure it drains