7 Replace the component immediately as it
will cause rapid corrosion of metal parts
sharing the same bilge water.8 Another possible source of the voltage
reading could be a stray, unterminated
conductor lying in the bilge or a con-
nected conductor with bad insulation.This chapter has touched on some of the
classic and routine tests you or a marine elec-
trician can use to confirm that your boat’s
electrical system, which is tied into the
cathodic protection system, is in good order.
These relatively straightforward tests will also
help you determine if you need to call in a cer-
tified corrosion specialist.118 electrical systems troubleshooting
A typical bonding system, showing locations to test with the amp clamp while activating DC circuits, to see if any stray cur-
rent exists. (Reprinted with permission from Boatowner’s Mechanical and Electrical Manual,third edition, by Nigel Calder)boat at only one through-hull point, bypassing
the others. Perform this test as follows:1 Partially flood the bilge with salt water.
2 Set your DVOM to DC volts.
3 Attach the negative or “com” lead to the
engine or battery ground (negative
terminal).4 Activate the suspect bilge pump and use
the positive lead as a probe.5 Tracking through the bilge water, slowly
home in on the float switch or pump, as
shown in the illustrations opposite.6 If you start to get a voltage reading on the
meter, you’ve found a leaking component.