More of this Feature • Part 1: Open Circuit Voltage • Part 2: Submerged Outboard, and More
Related Resources • Maintenance Q&A Index

What is the open-circuit voltage of a 12-volt battery, and how can you test for it? V.L., via e-mail
Open-circuit voltage is what is measured when a battery is not delivering or receiving power. For a fully charged 12-volt battery, the reading should be 12.66 volts, or 2.11 volts per cell.

To check the open-circuit voltage of your battery, first disconnect the battery cables so that no power is coming in or going out. Set your multimeter to read "DC volts" (for meters without auto ranging, set the scale to 20 volts), and touch the red (positive) probe to the positive battery terminal and the black (negative) probe to the negative terminal as shown here. If the reading is below 12.66 and the battery has been fully charged, one or more cells may be damaged or may have excessive sulfite buildup on its plates. A hydrometer test for each cell will determine which, if any, is bad. Placing the battery under an equalizing charge can remove sulfite buildup on the plates. Check with your battery manufacturer for the correct way to perform this procedure.

While getting ready to transport our tender's outboard, it slipped into the water. We retrieved it quickly but are worried about possible damage from the saltwater submersion. What is the procedure for cleaning it up? J.H., via e-mail
First, rinse the outside of the outboard with clean, fresh water. Then remove the cover and rinse off the engine. If you have access to compressed air, blow the water off all exterior surfaces; if not, thoroughly wipe down the engine.

Now use the compressed air--in this case, canned air will do--to blow off water and residue from around the plug(s). Disconnect the plug wire(s) by twisting the boot back and forth while pulling; pulling on the wire instead of the boot may cause internal damage to the wire. If the plug is difficult to remove, apply penetrating oil--Liquid Wrench or WD-40--around the plug threads, and let it soak for about ten minutes.

Remove the plug(s) with an appropriate socket wrench. Upon reassembly you should replace them with new ones of the correct heat range and gap. Drain as much water as possible from the power head by placing the outboard in a horizontal position and manually rotating the flywheel with the spark plug hole(s) facing downward. Next, pour rubbing alcohol into the carburetor throat(s) to displace any water in the intake system. Manually rotate the flywheel at least one full turn, then position the engine so you can pour more rubbing alcohol into the spark plug hole(s). Manually rotate the flywheel another full turn. You can now install the new spark plug(s).

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