A Change in Element Page 2

Maintenance Q & A — April 2005
By Capt. Ken Kreisler

A Change in Element
Part 2: Freshwater pump failure, and more.
 More of this Feature
• Oil filter maintenance, and more
• Water pump failure, and more
• PMY Tries... Taylor Made Instrument Covers

 Related Resources
• Maintenance Q&A Index

How do I test a battery that does not keep a charge? N.H., via e-mail
First fully charge the battery and let it sit for about 15 minutes to allow any surface charge to diffuse to make sure you get a proper reading. You can also remove a surface charge by putting a heavy load on the battery for about 30 seconds.

Remove any leads or battery cables, and read the voltage with a voltmeter. The result is the battery’s open-current voltage. If it’s less than 12.4, you most likely have a bad cell. Next check the specific gravity of each cell with a hydrometer.

Leave the battery in the open-circuit mode for three days and then retest for both open-circuit voltage and specific gravity. If the open-circuit voltage drops by 0.2 or the specific gravity drops by 0.035 in one or more cells, you should replace the battery.

There could be any number of causes for the battery’s failure, but most likely it’s due to a short in one or more of the cells. This is often due to repeated deep discharging. To prevent this, avoid discharging your battery to beyond 50 percent of its capacity.

I had a freshwater pump failure and found that the impeller had some deposits on it and the pump housing. What is this, and how can I prevent it from happening again? L.V., via e-mail
All water, except distilled, contains minerals and other contaminants. Depending on your geographic location, these can include calcium carbonate, calcium sulfate, iron, copper, silica, and lead. When these minerals and contaminants are heated along with the water in your engine, they can separate out and form deposits like those you’ve found. The water’s pH and “hardness” will also affect the accumulation of deposits.

Left unchecked, these deposits can cause corrosion. Moreover, an accumulation of only 116 inch has the same insulating quality as four inches of cast iron. The result here is a reduction in heat transfer that can be severe enough to cause engine damage.

While it’s impossible to remove all the contaminants, there are some things you can do to reduce deposit formation. Use only distilled or deionized water, and follow your engine manufacturer’s specifications regarding the correct coolant ratio, the use of additives, and coolant change intervals.

One more thing: As you’ve had a problem with your impeller, be sure to check the integrity of your cooling system. Inspect the water-pump seals and all hose connections for weeping and leaks. Since you’ve most likely lost coolant when changing the impeller, this may be a good time to drain, flush, and refill the entire system. Before using any flushing additives, refer to your engine manual. And be sure to use plenty of absorbent pads under your engine to prevent spills.

Need help with a maintenance problem? Write to Maintenance Q & A, Power & Motoryacht, 260 Madison Ave., 8th Fl., New York, NY 10016. Fax: (917) 256-2282. e-mail: ken.kreisler@primedia.com. No phone calls, please.

Next page > PMY Tries... Taylor Made Instrument Covers > Page 1, 2, 3

This article originally appeared in the April 2005 issue of Power & Motoryacht magazine.

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