Antifreeze question - IAT or OAT

[bruceb58]

On my current engine, I use the Volvo NeutraSalt system. I run the system right before I pull in from salt water and I use it again after I flush my motor if I have been in salt. That way, there is neutra salt solution sitting in the block. It is definitely helping my manifolds last longer.

In the future, my engine will rarely go in salt. I am going to be retiring and the boat will sit at my dock in Lake Tahoe all summer.

 

[Lou C]

No Title

My boat came from the mid west according to the previous owner and it had a marina sticker from Indiana on it where it was initially sold. It has been used in salt water probably between 17-18 years total. When a total repower is needed with a new crate engine I am going to investigate if the Cobra impeller puts out enough volume of flow to run a full closed cooling system. That way every 5/7 years I only have to replace the exhaust risers instead of the manifolds as well. If not I'll just do the half system and keep replacing the exhaust as I have. Two sets of OMC batwings in addition to the ones that came on it and then the latest set which is a Volvo/late OMC center riser style....

​I have heard good things about the Neutra-Salt system, for my use the best thing I can do is good flushing at the end of the season and then fill it with PG antifreeze with corrosion inhibitors, because the Neutra-Salt system will only work with an engine mounted impeller like Volvo's I think....

​PS Bruce I just retired myself, but staying here in salty Long Island....

 

[bruceb58]

If you really wanted to go with a full closed system, just mount an engine driven water pump and put an inlet through the hull.

NeutraSalt does only work with an engine driven pump. It needs to feed on the suction side of the pump.

 

[stonyloam]

OK for rust to form you need three things: exposed iron, water and oxygen. In an engine that has been run for a year all of the exposed iron will be coated with a layer of rust. So in a drained engine block you will have no (or almost no) exposed iron, you will have moisture and if you put the plugs back in, very little oxygen (only that in the air trapped in the engine block) and if any rusting does occur the oxygen will be consumed and will stop. The result would be only an insignificant (a few grams at most) amount of rust. Being cold actually slows rust formation. The hot water that you run through the engine all summer contains a significant amount of O2 (that is what fish breath) and is constantly replenished so it is quite good at causing rust. Now I am not saying that adding antifreeze to prevent corrosion is bad, just that it is unnecessary.
Now some of you say ? I put some antifreeze in the freezer and it froze?. The difference between water and antifreeze is that water expands and causes block damage when it freezes and antifreeze does not, at least to -50 or -100 F depending on what you get. So if you properly drain the block then add antifreeze you will be OK, but if you try to DISPLACE the water with antifreeze by adding it through the outdrive it is a crapshoot. I sure love my 470 this time of year

 

[bruceb58]

OK for rust to form you need three things: exposed iron, water and oxygen. In an engine that has been run for a year all of the exposed iron will be coated with a layer of rust. So in a drained engine block you will have no (or almost no) exposed iron, you will have moisture and if you put the plugs back in, very little oxygen (only that in the air trapped in the engine block) and if any rusting does occur the oxygen will be consumed and will stop. The result would be only an insignificant (a few grams at most) amount of rust. Being cold actually slows rust formation. The hot water that you run through the engine all summer contains a significant amount of O2 (that is what fish breath) and is constantly replenished so it is quite good at causing rust. Now I am not saying that adding antifreeze to prevent corrosion is bad, just that it is unnecessary.
Now some of you say “ I put some antifreeze in the freezer and it froze”. The difference between water and antifreeze is that water expands and causes block damage when it freezes and antifreeze does not, at least to -50 or -100 F depending on what you get. So if you properly drain the block then add antifreeze you will be OK, but if you try to DISPLACE the water with antifreeze by adding it through the outdrive it is a crapshoot. I sure love my 470 this time of year

Good explanation.

 

[crazy charlie]

cashwowud,I would 100% add the antifreeze for the reasons you mention.I have done that for 30 years and will never be convinced to leave dry for a very simple reason.I have seen manifolds and risers grow waaaay more rust in them just sitting in my garage for 6 months than the entire time they were on my boat.They came off the motor very clean after 10 years .Could have put them right back on .They grew so much rust sitting in my garage for a few months ,I didnt recognize them as mine.

 

[Scott Danforth]

neutra salt or salt-away can be used on muffs for non-engine mounted applications. I do it on my boat every outing. I also spray the trailer with the salt-away mix and then rinse after every outing.

 

[cashwowud]

Thanks everyone for your replies. It seems to me that putting antifreeze in the block for corrosion reasons may or may not do any good and the only way to prove it would be proper scientific tests but it certainly won't do any harm.

cashwowud

 

[bruceb58]

I had a set of manifolds I took off my engine when I decided to replace. They sat outside for 4 years before I finally got around to throwing them in the trash. They pretty much looked the same as the day I took them off.

 

[Lou C]

Are you in a dry climate or a damp one?
​Here it is damp most of the time and exposed cast iron rusts very fast. When I was doing my top engine overhaul, with the cyls heads off and the block in the boat I had to coat the cyls with fogging oil or else they would start to rust in a few days, even with a good cover on the boat. This is why I always fogged the engine every fall.

​PS I called Orca Marine about closed cooling systems the other day. I asked how many GPMs you need for a full system and they said it takes about 30 GPM. So when I have the boat up and running next spring I'm going to measure the exhaust water coming out under the transom (30 gal/min means it should fill a 5 gallon bucket in about 10 sec right?)

​PPS I took 2 sets of my old OMC Batwings to the re-cyclers instead of throwing them out, you only get about 6 cents per lb for cast iron so I got maybe 11 bucks for both sets!

 

[bruceb58]

Not super dry..we get ocean influence. Dry in summer. They were out in rain too.

 

[QBhoy]

OK for rust to form you need three things: exposed iron, water and oxygen. In an engine that has been run for a year all of the exposed iron will be coated with a layer of rust. So in a drained engine block you will have no (or almost no) exposed iron, you will have moisture and if you put the plugs back in, very little oxygen (only that in the air trapped in the engine block) and if any rusting does occur the oxygen will be consumed and will stop. The result would be only an insignificant (a few grams at most) amount of rust. Being cold actually slows rust formation. The hot water that you run through the engine all summer contains a significant amount of O2 (that is what fish breath) and is constantly replenished so it is quite good at causing rust. Now I am not saying that adding antifreeze to prevent corrosion is bad, just that it is unnecessary.
Now some of you say “ I put some antifreeze in the freezer and it froze”. The difference between water and antifreeze is that water expands and causes block damage when it freezes and antifreeze does not, at least to -50 or -100 F depending on what you get. So if you properly drain the block then add antifreeze you will be OK, but if you try to DISPLACE the water with antifreeze by adding it through the outdrive it is a crapshoot. I sure love my 470 this time of year

Except the block isn?t sealed when you put the plugs back in. How can it be ?

 

[QBhoy]

The statement about being cold slows rust formation is not true. It?s surely the opposite. Cold corrosion

 

[bruceb58]

The statement about being cold slows rust formation is not true. It’s surely the opposite. Cold corrosion

It's a chemical reaction. Heat increases the rate of the chemical reaction.

 

[QBhoy]

Completely disagree Bruce. Lower temps in damp conditions encourage corrosion

 

[JoLin]

I'm with Bruce. Cold inhibits chemical reactions (of every type I can think of), heat encourages them. I fill the block and heads with AF. Does it help? Maybe, maybe not... but I know it won't cause any harm and it makes me feel like I've gone the extra mile and done about everything I can in that regard. To me it's worth $35. per engine once a year. Your opinion may vary

My .02

 

[QBhoy]

When I say cold...I suppose I don?t mean freezing cold. I forgot you guys get serious sub 0 temps sustained. The average temperature of the innards of a boat in winter here is likely well above freezing.

 

[QBhoy]

But I sure don?t agree that the engine cooling void is sealed when the plugs are put in. Surely no one would argue seriously that they are.

 

[bruceb58]

Completely disagree Bruce. Lower temps in damp conditions encourage corrosion

BS...MY time as a chemistry major taught me a few things! Every degree temp lower slows down a chemical reaction...in this case, it's oxidation.

Google is your friend if you don't have time to major in chemistry like I did for awhile.

 

[bruceb58]

Here...I looked up one for you:
https://link.springer.com/article/10.1023/A:1016021815596

The first is that corrosion may be significantly different at one constant temperature compared to another for a given water quality. For example, a pipe at 25 ◦C (72 ◦F) may experience more corrosion problems than a pipe at 5 ◦C (40 ◦F).