Q & A — April 2005
By Capt. Ken Kreisler
A Change in Element
2: Freshwater pump failure, and more.
How do I test a battery
that does not keep a charge? N.H., via e-mail
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
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: firstname.lastname@example.org. No phone calls, please.
This article originally appeared in the April 2005 issue of Power & Motoryacht magazine.