Author Topic: Speaking of resistors....... (Read 7577 times)

Jason · « **on:** April 25, 2011, 10:59:12 PM »

I just noticed this today. My coil says "use with external resistor" but my engine does not have a resistor. I have been running it htis way for 5 years since I got the boat and for who knows how long before that. Is my resistor hiding? Or do I have the wrong coil?

Jerry · « **Reply #1 on:** April 26, 2011, 01:16:22 AM »

Looks like you have 2 wires going to the + side of the coil. One should be 12V for starting from the solenoid, the other should be a resistor wire from the switch.

Tonka Jim · « **Reply #2 on:** April 26, 2011, 06:14:38 AM »

Jason,

The ballest resistor on my 120 is on the port side of the engine, near the block & manifold drain plugs.

Rich_V174SS · « **Reply #3 on:** April 26, 2011, 06:37:34 AM »

If you don't have a visible ballast resistor then your engine is equipped with a resistance wire, so it still does have an external resistor.

Are you still running with points in the distributor or a Pertronix setup?

Jason · « **Reply #4 on:** April 26, 2011, 07:23:08 AM »

I am running points. Good old reliable points!

It must have a resistance wire. I don't remember seeing anything on the otherside of the engine but maybe I missed it.

I suppose i can just check the voltage at the coil with the key on (not cranking) and if it's 12V then no resistor. correct?

Rich_V174SS · « **Reply #5 on:** April 26, 2011, 07:59:10 AM »

Yes, voltage at the (+) terminal of the coil will be a little less with a ballast or resistance wire. Just another quick question... the red wire in your pic going from the distributor to the coil which I assume is attached to the points/condenser, which terminal on the coil is it connected to, (+) or (-)?

Jason · « **Reply #6 on:** April 26, 2011, 09:53:08 AM »

The red wire is on the ground side of the coil. I know it should be black. I think they swapped it out when the previous owners put in the new points. The other two wires on the negative side must go to the tach and

?.

Green with Envy · « **Reply #7 on:** April 26, 2011, 11:28:46 AM »

Supreme Marine told me last year when I had the boat in for service that my coil was wired backwards (and it still ran!). They switched it for me. I have 9v at the coil wire. I do not recall a resistor anywhere on the engine. I can check when I get home tonite on both engines to see what turns up.

Jason, I have the allignment tool from Jeff in my trunk.

Rich_V174SS · « **Reply #8 on:** April 26, 2011, 01:02:20 PM »

Quote from: 74GlasCarlSS on April 26, 2011, 09:53:08 AM

The red wire is on the ground side of the coil. I know it should be black. I think they swapped it out when the previous owners put in the new points. The other two wires on the negative side must go to the tach and ?.

The other wire on the negative side of the coil probably goes to the shift interrupter switch, which when activated by shifting from gear into neutral shunts the coil to ground momentarily killing the engine so your gears can disengage.

Rosscoe · « **Reply #9 on:** April 26, 2011, 05:44:34 PM »

Looks like Jasons motor has that unknown (to me) black round component too. Right by his fuel filter. What is that?

Rich_V174SS · « **Reply #10 on:** April 26, 2011, 05:50:13 PM »

That's the oil pressure sender, it reports the oil pressure to the gauge. I just replaced that on my engine because it was registering full oil pressure all the time when the motor was running, pegging the meter. Now it works like it should sensing pressure in varying amounts depending on engine speed.

Rosscoe · « **Reply #11 on:** April 26, 2011, 06:28:17 PM »

OK an answer to that mystery.

Jason · « **Reply #12 on:** April 27, 2011, 09:48:49 PM »

I am getting 12.5V at the coil so I must not have a resistor. Think I should either put in a coil with a resistor or install just the resistor? or leave it and take my chances...

Rich_V174SS · « **Reply #13 on:** April 28, 2011, 07:04:44 AM »

Are you sure you don't have a resistor mounted someplace on the other side of the engine, perhaps underneath the manifold? When the engine is running and the alternator is charging your coil could be receiving 13.8+ so it should have a resistor or else it might get really hot and start breaking down. If you disconnect the two wires on the (+) terminal of the coil and check voltage on them individually with the key on, the one with power should be the one with resistance. Check it against another live 12v source to see if there's a difference. The other wire at the (+) terminal would be the bypass coming from the solenoid mounted near the harness connector, leave that alone. Does your engine have an electric choke? If it does the resistance wire was usually connected between the choke and the coil, leaving the choke unaffected.

Jason · « **Reply #14 on:** April 28, 2011, 09:12:08 AM »

There is no resistor block anywhere on this engine. All the wiring diagrams I see show a resistor wire but also show it as purple which my wire is not. I cheked it with Key on, engine off. I'll do some more checking. Maybe let it run and see if the voltage drops. Maybe the resistor wire needs to "heat up".

No electric choke. I run some of the checks you said Rich.

Tonka Jim · « **Reply #15 on:** April 28, 2011, 02:08:56 PM »

Jason,

I'll look at the 140 in the shed, I'm sure the wiring is original.

Jason · « **Reply #16 on:** April 28, 2011, 08:09:28 PM »

I looked at mine more today. I do have a resistance wire. It says so directly on the wire where it connects to the coil. Why I am getting 12V is beyond me. Next time I fire it up I'll check it when it's running and warmed up. I have a feeling the wire needs to warm up. I also compared my wiring to the manual and it matches it exactly and I am sure it is the factory wiring.

On a side note. Why are there two oil pressure senders? Looks like one is a sender and the other is a switch according to the wiring diagram.

Rich_V174SS · « **Reply #17 on:** April 28, 2011, 08:19:17 PM »

Quote

Why are there two oil pressure senders? Looks like one is a sender and the other is a switch according to the wiring diagram.

The other is a switch to trigger either a warning horn or light when there's no oil pressure. No oil pressure closes connection in the switch to engine ground completing the circuit to enable it's attached warning device.

Rosscoe · « **Reply #18 on:** April 28, 2011, 08:23:05 PM »

I'm getting over 12 volts on the coil terminals, WITH a resistor.

Rich_V174SS · « **Reply #19 on:** April 28, 2011, 08:31:36 PM »

I wouldn't worry about. If you haven't lost the coil yet then chances are you're not going to.