How much antifreeze to protect engine

[John T1594]

Yes, it’s only the end of July but I will have to haul and winterize my boat in about 5-6 weeks. The winter temperatures in central NJ can reach only a few degrees below zero but usually stay above zero. To winterize my engine (3GM30F) I let the engine raw water pump draw 3 gallons of the blue (-100) propylene glycol antifreeze, undiluted, through the raw water side of the cooling system. This has always been adequate and I thought I was adding more than needed. This spring, I had to have my U-shaped exhaust mixing elbow replaced after 500 hours on my Yanmar. The mechanic noted that the elbow was cracked and asked about how much antifreeze I use to winterize the engine. So what is the consensus on how much antifreeze to run through and safely winterize the engine? My exhaust thru-hull port is hidden under the hull at the waterline so I cannot see the color of the antifreeze leaving the exhaust. The blue color of the antifreeze also makes it difficult to see.
BTW: With the new exhaust mixing elbow, the engine runs about 5 degrees cooler at all RPM’s this season than in the past. I always operate my engine at 2,900-3000 RPM and thought that would prevent clogging of the elbow.

 

[Don Crowther]

I'm pretty sure that there is no anti-freeze in the elbow since this is the high point of the system. At least it is on my boat.
I put 1.5 gallons of anti-freeze though my exhaust with no problems and it gets alot colder up here

 

[splax]

I disconnect the raw water intake hose and place it in a gallon or so of the red biodegradable antifreeze. When the antifreeze comes out the exhaust you're protected.

 

[smoothsailing]

Yanmar manual says to fill a bucket with 5 gal of AF and run all of it thru the heat exchange/exhaust.

I have been using the RV AF in my Atomic 4 and now my Yanmar with no problems.

 

[Don Lucas]

I use the green stuff for the engine. The only place that red RV stuff should used is in the potable water system as it is bad for rubber and plastic.

 

[thinwater]

a. It sounded like he was winterizing in the water (said discharge was under the hull).

b. The is NO substitute for measuring the freeze point of the AF as it comes out. Otherwise, you don't know how much water was in the system. Going by color is asking for cracked elbows; the visual appearance of dye is NOT linear with concentration.

c. The local temperature is not a reason to reduce the concentration. If I lived in the south I would either pickle or drain.
1. Corrosion additives are less.
2. if the gycol is less than 25% (-40 BP is about 33%) it can easily ferment and go acid. If you check the glycol people leave for recycling in the spring, much of it smells like wine gone bad. This is acidic (engine) and nasty (freshwater). Pickle the systems properly with 30% glycol the whole way through.

If you do not have a refractometer (measures EG, PG, and battery SOC), you need one.

---

Or be penny wise and pound foolish. One bit of damage or the frustration of not being able to drink the water will buy a lifetime supply of AF.

 

[JK_Boston_Catalina310]

I am going to second Thin Water. Go on Amazon and buy a refractometer that test antifreeze. Mine does antifreeze and lead acid battery specific gravity and it cost less than $50. Test the antifreeze before it goes in. Run it through the engine until you get the same strength out. And only use good antifreeze, not the discount stuff at the box store.

My friends always wondered why I had no issues with winterizing. I do this on my engine and my freshwater system. Never had an issue no matter how cold it got. Can't take credit. I learned it from Maine Sail.

 

[Maine Sail]

a. It Sounded Like He Was Winterizing In The Water (said Discharge Was Under The Hull).

B. The Is No Substitute For Measuring The Freeze Point Of The Af As It Comes Out. Otherwise, You Don't Know How Much Water Was In The System. Going By Color Is Asking For Cracked Elbows; The Visual Appearance Of Dye Is Not Linear With Concentration.

C. the Local Temperature Is Not A Reason To Reduce The Concentration. if I Lived In The South I Would Either Pickle Or Drain.
1. Corrosion Additives Are Less.
2. If The Gycol Is Less Than 25% (-40 Bp Is About 33%) It Can Easily Ferment And Go Acid. If You Check The Glycol People Leave For Recycling In The Spring, Much Of It Smells Like Wine Gone Bad. This Is Acidic (engine) And Nasty (freshwater). Pickle The Systems Properly With 30% Glycol The Whole Way Through.

If You Do Not Have A Refractometer (measures Eg, Pg, And Battery Soc), You Need One.

---

Or Be Penny Wise And Pound Foolish. One Bit Of Damage Or The Frustration Of Not Being Able To Drink The Water Will Buy A Lifetime Supply Of Af.

+1,000,000,000 ..!!!

 

[quadrille38]

Just finished winterizing today. I use the 100 below RV stuff (it was blue in color) for the fresh water side of the engine. Ran a 5 gallon bucket through to make sure the muffler and system were flushed. The engine side of the cooling system uses regular automotive type antifreeze. For the plumbing, I bypass the water heater, run the -50 pink stuff through the faucets. Takes about 3 to 4 gallons to do the galley, head sink, head, shower sump pump and the transom shower. Then I hook up an air compressor and blow the lines out.

I also make sure to run the bilge pump and pump the hand bilge pump to make sure any water in those lines is flushed out.

 

[Scott B]

Just finished winterizing today. I use the 100 below RV stuff (it was blue in color) for the fresh water side of the engine.

You mean the Seawater or raw water side. The Fresh water side in the enclosed coolant the runs through the engine and heat exchanger. The Seawater side is drawn from the lake or sea. The terms are sometimes confusing, and even more so since here in the Great Lakes the water is mostly "fresh"

 

[quadrille38]

You mean the Seawater or raw water side. The Fresh water side in the enclosed coolant the runs through the engine and heat exchanger. The Seawater side is drawn from the lake or sea. The terms are sometimes confusing, and even more so since here in the Great Lakes the water is mostly "fresh"

Yup we have fresh water here LOL

 

[John T1594]

Yes, Yes, all the above suggestions are good ones but I am puzzled as to how to measure the antifreeze as it comes out of my exhaust. I have one of those "sugar scoop" transoms in my 2000 H340 and the exhaust port is at or just slightly above the waterline and under the hull. If I stand/kneel on the swim platform to reach the exhaust, the port is below the waterline. I am not about to disconnect the exhaust hose and vent it overboard as part of my winterizing ritual.

As to the cracked exhaust elbow, well, it had 500 hours on it and I think I got my money's worth out of it. Since it is the highest point in the exhaust and cooling system I doubt that it would have any water in it and should have been well protected after three gallons of the -100 antifreeze. Nonetheless, I will add another gallon or two to my engine winterizing to be on the safe side