DON’T HESITATE TO RENOVATE B Y C A P T. F R A N K L A N I E R
Don’t Be Cavalier About Coolant What every boat owner should know about coolant. hen most boat owners think about their engine coolant, they typically check the reservoir, see some kind of fluid sloshing around in there and call it good. It’s a cavalier approach to something so crucial to the proper operation and long life of your engine. Here’s how to ensure your coolant is up to the task.
Exceeding an 80% concentration of antifreeze can result in silicate gelling.
CAPT. FRANK LANIER is an award-winning journalist, boat maintenance guru and owner of Capt F.K. Lanier & Associates, Marine Surveyors and Consultants:
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What’s in a name? The correct term for the glycol-based heat-transfer fluid used in engines is coolant, a mixture of water and ethylene glycol (EG). This naming distinction between antifreeze and coolant was made decades ago to clarify that engine coolants can be used year-round to protect against both freezing and overboil. While the word antifreeze is often used to describe the ethylene glycol portion of engine coolant, it’s primarily used to describe a propylene glycol (PG) solution designed specifically for winterizing fluids or systems, such as your boat’s freshwater systems. PG has low toxicity, however EG is poisonous and must be handled with caution. While all coolant provides engine freeze protection, not all antifreeze solutions are suitable for use as engine coolants. In other words, that pink stuff used to winterize your potable water system can also be used to winterize the open or raw water side of your engine cooling system, but it’s not suitable for the closed portion. Conversely, engine coolant should never be used to winterize potable water systems due to its toxicity. It’s all about the mix Most engine manufacturers recommend a 50/50 mixture of antifreeze (about 48% glycol) and water for optimum year-round protection. Straight EG freezes at around 8 degrees Fahrenheit, boils at 330 degrees Fahrenheit and is around 15% less efficient at carrying heat away than water. A 50/50 mix provides freeze protection down to minus 34 degrees Fahrenheit and overboil protection to 228 degrees Fahrenheit. A more concentrated glycol solution will increase freeze protection, but reduces cooling ability, while a more diluted mixture reduces corrosion protection. The only way to verify the proper ratio of antifreeze to water is to measure the concentration of antifreeze with a floating ball gauge, hydrometer, test strip or
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Propylene glycol is non-toxic and suitable for winterizing potable water systems.
refractometer. Simply opening the reservoir cap and dumping in extra antifreeze in efforts to increase freeze protection will likely result in a mixture with too much antifreeze. Exceeding an 80% concentration of antifreeze can cause silicate gelling, where the silicate corrosion inhibiting additives found in most antifreeze drops out of suspension, forming a greenish goo that clogs the system and reduces heat transfer. If gelling occurs, the system must not only be drained, but fully flushed before adding new, properly mixed coolant. If water needs to be added, use only distilled water, which contains no acids, salts or minerals and is pH neutral, all of which help maximize coolant service life. Preventing corrosion While the rate of corrosion inside your engine depends on a number of factors, a prime consideration is the pH of the coolant itself. Corrosion-inhibiting additives are mixed into the coolant to make it more alkaline and it will continue to protect your engine from corrosion as long as it remains that way. To keep coolant pH alkaline for a reasonable length of time, it must contain enough corrosion inhibitor to neutralize the acids formed from glycol degradation, which occurs as the coolant ages. This coolant neutralizing capability is called “reserve alkalinity.” How long it lasts depends on the quality and type of additives used in the antifreeze, as well as factors such as heat, impurities and dissolved oxygen, all of which can deplete these inhibitors over time. The goal of the boat owner is to monitor the coolant and change it before all the reserve alkalinity has been used up. You’ll want to follow the guidance provided by your engine manufacturer but, in general, coolant should be changed every five years or after 1,000 hours of use. ★
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