I'm not sure who told you that the proper marine antifreeze will promote corrosion - that is just plain wrong. The correct antifreeze contains corrosion INHIBITORS. Draining it, however, WILL allow for corrosion. Besides, just draining doesn't evacuate all the water. I'm keeping this short since there's lot's of threads on this subject already. Probably more information than you would ever need to know.

 

you will get many opinions on this. i personally always drained the block without any antifreeze and never ever had a problem.

draining gives the best protection from a nightmare of a cracked block , antifreeze helps with preventing corrosion.

when going antifreeze make sure your tstat fully opened and make sure the mixture is enough for your winter temperatures.

be aware you have liquid in the block over the freezing winter and there are boaters who learned the very hard way next spring when they messed up with this kind of winterization.

best regards

 

Does anyone have any thoughts on draining the block, manifolds and hoses after winterizing? The Mercruiser manual for my 2001 raw water cooled 5.0 EFI Bravo3 seems to suggest filling the system with propylene glycol but doesn't require it. Many popular boat sites recommend leaving the system drained because "air doesn't freeze". On the other hand marine engine antifreeze contains water which promotes corrosion. I am interested in knowing what others on this forum do.

Thanks for the help.

The first season I owned my 330 I had a marine service perform the winterization on my motors (raw water cooled). They drain the block and cooling system fully after running antifreeze thru it. The next year I did it myself the same way and didn't have any problems. I did the same thing last week to the engines for the upcoming winter season.

 

Yup, running antifreeze through the engine from a bucket will NEVER cause any problems. Apparently I'm just making this stuff up. And apparently the couple of blocks we replace every Spring for people who used the bucket method is a fantasy.

 

I guess if your doing that in a climate controlled environment OK. If not, I've never understood the "drain it and leave it" approach. I think we all know what happens to our tools left exposed to air outside for 6 months. This also happens to the innards of your engine. Antifreeze also contains lubricants to keep all those spinning bits happy as well.

 

I actually think the bucket method should be OK as long as the engine is properly drained prior to putting the antifreeze in. If water is in the engine something is going to bust if it sees cold enough temps. The fact is the majority of engines that are just drained/no antifreeze do not freeze and there's a lot of them that see cold enough temps. To me that implies for some reason the water was not completely drained before being put up. Maybe that's as simple as some accumulated rust holding back some water. So maybe that's the 'ah ha' for putting in antifreeze. Cool man, I took that right around the loop

 

I actually think the bucket method should be OK as long as the engine is properly drained prior to putting the antifreeze in.

You're right, it can be. But the step that most people skip is the removal of the t-stat. That's they only way to assure that the antifreeze gets everywhere and pushes out the last little bit of standing water. My post above was out of frustration since it feels like I've gone over this a hundred times. But the reality is that when I do winterizations (the pour method), I very often see anywhere from 12 to 30 ounces of clear water being pushed out before the pink stuff. That is the water that was still trapped after draining. Whether the bucket method would push all of that water out is a crap shoot - you're taking a gamble on whether or not the t-stat stays open long enough. Not a gamble I want to take.

 

I appreciate everyone's responses, but my question wasn't really about how to introduce the antifreeze into the block/manifold, but rather whether leaving antifreeze in the cast iron engine would result in less corrosion of the internal block and exhaust manifold parts.

I can weigh in a little on the effectiveness of the bucket method to fill the block with antifreeze, since with my 1990 motor I had 7 years of winterization experience with running the engine on a bucket for winterization. My procedure was to run until the engine came well up to operating temp. , immediately switch over to the antifreeze in the bucket, and run until 6 gallons were sucked into the system. After that, I always pulled the drain plugs in the block and the bottom hoses from the manifolds to drain what I assumed was all of the liquid. Although this may seem like a waste of anitfreeze, I felt that it was a lot cheaper than replacing a cracked block. An engine that old has a lot of sand, rust, and misc. crap accumulating in the bottom of the block and I was afraid that if I didn't try to fill it with antifreeze, there would be pockets of water that would be trapped. As I said in my original post, I drained the block because I read on other sites that this was the safest way to protect the block from freezing (although not necessarily from corrosion). I can say without a doubt that there were at least 2 years when the water that drained from the block (after I supposedly filled it with antifreeze from the bucket) showed significantly less color coming from one side of the block than the other. That tells me that the antifreeze did not circulate evenly on both sides of the engine, and the dilution ratio was different. I don't know if this would have resulted in so much antifreeze dilution that one side of the block would have suffered from freeze damage that year, but it was certainly food for thought for me.

Back to my original question, I am still concerned that leaving a quality antifreeze that is somewhere between 60% and 40% water (yes water ... read the MSDS for commonly available winterizing antifreezes) in contact with the cast iron parts of the engine has the potential to introduce corrosion that would not happen if the propylene glycol (which was poured into the manifold hoses and the block directly) was drained. I understand that marine winterizing antifreeze (which I always use) contains "rust inhibitors", but the proportion used is extremely small (about 3%) and appears to have a limited protection life. (For anyone interested, the common inhibitor appears to be dipotassium phosphate which is used as much to buffer the effects of the glycol on the cast iron as to keep the block from corrosion).

 

Back to my original question, I am still concerned that leaving a quality antifreeze that is somewhere between 60% and 40% water (yes water ... read the MSDS for commonly available winterizing antifreezes) in contact with the cast iron parts of the engine has the potential to introduce corrosion that would not happen if the propylene glycol (which was poured into the manifold hoses and the block directly) was drained.

i guess nobody can answer you on solid facts , only on personal opinions. fact stays i never had and do not know anybody who had a rusted through block in the spring by draining it with the proof it would not had happened by using antifreeze. on my last boat with a volvo penta antifreeze was not recommended at all for freezing protection, mercruiser says its not needed but can be done.

if you boat in saltwater , flushing the engine with fresh water seems to be always a good idea - not only for winterization storage.

best regards

 

Mai Tai - I think you're entering into a dangerous thought process. By chance are you an engineer? Your line of questioning sounds like it. But, in essence, you're second guessing the engineers that were paid good money to develop a product to specifically combat a known problem. Forget about the "only 3%" thing - that means nothing. All that matters is that it's enough to do the job. The percentage doesn't matter - just that it's the appropriate amount.

Also, forget about the fact that there's water in antifreeze. That also means nothing. Again, all that matters is that the burst temperature for the product is appropriate. Your car has water in the cooling system - yet no one seems to question that.

As far as the corrosion aspect, I think it's a fool that thinks (or has at least been convinced by fools) that bare metal is less susceptible to corrosion than being immersed in a liquid specifically designed to combat corrosion.

Here's a fact: A few years ago I worked on a guy's boat in the Spring (he had winterized it and had drained the block). When I started it up, you should have seen the mass of rusty-colored water coming out. The incoming water was "de-rusting" the interior of the engine. It continued for probably a good minute or two until the rust was finally removed from the engine - at least to the point where I couldn't tell, anymore. I, as well as others here, have seen it a few other times, too. I have NEVER seen rusty-looking fluid coming out when running an engine that had the proper AF in it.

 

I am not a chemist nor an engineer but I did stay at a Holiday Inn last night I would also like to strengthen/clarify Dennis' point. I'm pretty certain that AF is not only a liquid but it's also a chemical.

An analogy: Our atmosphere has hydrogen (1%) and oxygen molecules (21%) etc, water (H2O) has hydrogen and oxygen molecules in it but if one gets enough H2O into ones lungs its not a good thing we can't handle H2O in our lungs even though H2O has oxygen and hydrogen in it (just like the atmosphere),

In AF the percentages of inhibitors, H2O and other chemicals all combine/bond to form a completely new chemical so forget the 40% water and only 3% inhibitors the water is no longer H2O. AF as a whole is a chemical designed to have an extremely low freezing point while protecting various types of metals from rust while lubricating rubber "o" rings, seals and gaskets etc. I hope this helps clarify the AF drain don't drain issue

H2O

 

Proper draining of water is important. My manual even says care should be taken that the boat is sitting level. I have the manual 3 point drain system, 2 plugs on the seawater pump and one in the distribution housing. The manual says that the plug in the thermostat housing must be pulled within 30 seconds of the others or it won’t drain properly.

 

I have no proof that an empty block will rust faster than one filled with proper antifreeze. Sure mine is only a little 3.0L, but it's all the same idea. Since my boat was new, I have followed the manual which says to add PG AF to help stop corrosion. After all the winterizing is done, (all water drained), I pull a few hoses off the thermostat housing and pour the antifreeze down these hoses. I leave the single point drain hoses disconnected until pink comes out and then reconnect and keep filling until the pink comes out the other end. 100% there is no water in there and the block/manifold are full of AF. After 7 months of storage, the pink gets drained before its maiden voyage, and the color looks as pink as when I poured it in. All I can see is the inside of the hose and a bit of the manifold interior and fittings. They all look super clean with no corrosion. Again, it may take 20 years for the manifold to rust out from the inside if left empty, but if adding AF helps the life of the engine, I don't mind spending the $10 extra.

 

Let me throw a wrench in here...
IMO...the pink stuff isn't good enough
I use the green Sierra -100 ENGINE antifreeze.. still environmentally sound
but has the corrosion inhibitors for ENGINES rather than for potable water systems.
and I would rather take a chance of a little dilution(you can only drain most of the water from a block)
in the -100 stuff as opposed to the -50 pink stuff.

 

Do what I do and have your marina or service technician winterize your engine and then you won't have to worry about it like I do

 

Mai Tia last seen June 3, 2019.. Just sayin

 

Gogiogo last seen today.

Just sayin

 

Gogiogo last seen today.

Just sayin

Sorry espos- wasn’t meant for you.

Was just giving gogiogo a heads up he may not get a response from Mai Ti since he stated this below.

“Mai Tai, I created a Clubsearay account just to answer your question”