Put to the Test
Q & A — October 2002
By Capt. Ken Kreisler
Put to the Test
| Bench-testing a solenoid, fixing a misfiring engine, checking for voltage drop, and more.
do I bench-test the starter solenoid on my 75-hp two-stroke outboard?
M.L., via e-mail
Begin by disconnecting the negative battery cable from the battery. Next remove all leads from the solenoid terminal studs. There is no need to remove the solenoid from the engine. Connect an ohmmeter--calibrated on the Rx1 scale--to the two large terminal studs (1 and 2 above, in both illustrations). The ohmmeter should indicate no continuity, due to the fact that no power is running through it. Replace the solenoid if any other reading is noted.
Using jumper cables, attach a 12-volt battery to the two small solenoid studs (3 and 4, above)--polarity is not important. You should hear a click as (or if) the solenoid engages, and the ohmmeter should indicate continuity. This is because the solenoid is a high-amperage switch that when energized shows a closed circuit. Replace the solenoid if any other reading is noted.
When you are finished, replace all the leads and connect the negative battery cable last.
having a steady misfire on my gasoline stern drive. What can I do to find
the problem? P.A., via e-mail
think I've got a voltage drop in the circuit that takes care of
my entertainment system. How do I test if this is the case? C.H.,
Since the circuit must be operating, turn on your entertainment system. Next, set your multimeter to D.C. volts. As the component being tested must be between the meter's two probes, place one of the probes on one side of the component and the other probe on the other side. If your meter reads zero volts, the voltage drop does not exist at that component. Repeat this procedure for every component on that particular circuit. A voltage drop will be indicated when the meter reads voltage. Usually, depending on load, a voltage drop greater than 0.5 volts indicates a problem.
the culprit, long runs of undersized wiring can cause excessive voltage
drops, so check your wiring runs and, if necessary, increase the wiring
size. In addition, as heat is generated with voltage drops, you may want
to check your components for excessive heat. Once you've isolated
the culprit, have it cleaned, repaired, or replaced.
This article originally appeared in the October 2002 issue of Power & Motoryacht magazine.