Voltage drop - watch that old wiring

[joe_db]

A lot of the wiring in my boat is new, but not all of it. The original 1973 wire runs back to the engine panel and forward again and so far seemed to have no issues. Well yesterday I noticed the engine running a little hot and the fuel pressure a little low. Hmmm
I kicked on the extra coolant pump and the extra fuel pump and noticed an odd thing - the pilot light on the panel that indicates a circuit being on for the fuel pump was dim and flickering. Time to whip out the voltmeter and find the fuel and coolant pumps were getting a grand total of 10 volts Note the top switch is before the run to the engine panel and back and the second fuel pump switch is after the run.
I am going to replace that wire run with new 10 gauge wire and then check and see if the ignition switch itself needs replacing too. Rust never sleeps and I guess corrosion only takes short naps, just because some old wire was good last year does not mean it is this year

[JOHN COOKSON]

Originally Posted by joe_db

Rust never sleeps and I guess corrosion only takes short naps, just because some old wire was good last year does not mean it is this year

Yes.
One gets so use to things wearing out as they are used. On a boat you don't even need to use it. It just rots or corrodes away.
I got so sick and tired of the "installment plan" drill Joe mentioned I finally rewired the whole shebang. Problem(s) solved.

TRUE GRIT

[Dave Neptune]

Joe, do you have all of those pumps and the ign being fed through the "key switch"? If so the flickering could well be the switches integrity.
I would suggest the coolant pump be fed by a relay controlled by the keyswitch. That's quite a load.

Dave Neptune

[ndutton]

I load up my ignition circuit pretty heavily - without a single issue by the way - and still remain under 10 amps.

Ignition load = 3.4 amps
Alternator excite = 0 amps (single wire self excite)
Facet fuel pump = 1.6 amps
Johnson CM30P7-1 coolant pumps (2) @ 2.2 amps ea.= 4.4 amps
EWDS = 0 amps (by design, no draw unless triggered)
Blower is on a different circuit

Total ignition circuit load = 9.4 amps

[joe_db]

I did think of that and may do so. I already use the starter button to activate a relay near the starter so the solenoid current is not doing a round trip to the cockpit. Good idea - I know my car uses relays for that stuff.

[joe_db]

Originally Posted by ndutton

I load up my ignition circuit pretty heavily - without a single issue by the way - and still remain under 10 amps.

Ignition load = 3.4 amps
Alternator excite = 0 amps (single wire self excite)
Facet fuel pump = 1.6 amps
Johnson CM30P7-1 coolant pumps (2) @ 2.2 amps ea.= 4.4 amps
EWDS = 0 amps (by design, no draw unless triggered)
Blower is on a different circuit

Total ignition circuit load = 9.4 amps

Step 1 is old wire out and new wire in and I will see if there are remaining issues.

[Dave Neptune]

Joe, do a really good test of the key switch while wiggling the key. Just may turn up something.
9.4 amps at 12v is just over 11.25 amps at 10v ti get the same 0power or watts of energy. Relays especially sealed ones are very reliable and easy to trouble shoot too.

Dave Neptune

[tac]

It's easy to check the switch - close the switch to energize all connected loads, and measure the voltage drop across the closed switch contacts. If the drop is more than a volt, the switch contacts likely are bad. If you know the current through the contacts, or better, measure it, then calculate the contact resistance. Good contacts should have a resistance in the tenths of an ohm.