How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

bankbuster

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Well I bought a ballast resister for the motor described in title....where do I mount it....or how do I mount it. The resister has 4 prongs, 2 at each end. If I remember right I only need 2 prongs.....1 wire comes from terminal block and one from coil....? I assume I connect 1 to each end of ballester...? Where do I mount it? Will this resister get hot, brittle? Does it have current running through it that I should consider when mounting? Thanks so much for any and all help!
 

Frank Acampora

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

It would help to have a photo posted.

However: Yes, the resistor will get hot. It does have some current (meaning amps) passing through it. That is its job. It takes 12 volts and drops it to about 9 volts to increase the life of the coil. The extra 3 volts is shed as heat. Depending upon the resistor, again, yes one side is attached to the power source--in this case, the blue wire from the ignition switch. The other side is attached to the positive terminal of the coil itself. Mount it away from other wires because the heat can degrade insulation.

If it has 4 terminals, one set may be the bypass side (explained later. However, I am not that well versed in old auto electrics and you would need to check with someone else as to what terminals do what job.

Typically, when an old auto is started, there is such a large load on the battery that battery voltage drops to 9 volts. SO: to get full power and spark from the coil (for positive starting) it is designed to use 9 volts. When the engine starts, voltage returns to 12 volts which is too much for the coil so a ballast resistor is put in line.

NOW: If the ballast resistor is in line at starting, the already low 9 volts will drop to about 6 or so. THUS: On autos, a starting bypass is also incorporated in the circuit to maintain 9 volts at all times.

A smaller boat engine will not or may not drop voltage to 9 volts at starting but it still will drop it some.

ALL this to say: If you have trouble starting with the ballast resistor in the circuit you will need to incorporate a bypass too.
 

bankbuster

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

fixtheboats002.jpg

Here it is. Wires are right. How should I safely mount this....any ideas? Thanks again for the help. I am water bound after this.....yeeeeehahhhhhh!
 

Frank Acampora

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

Couple of washers behind it to space it away from the oil recirculation plant. Then use a long 1/4 - 20 bolt through it and the top recirculation plate bolt.

That looks like the old ceramic Chrysler automotive ballast resistor
 

bankbuster

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

You are correct Frank.....that resister is from a Cordova, 1977 i believe...lol. I have been told by many that they work exactly the same but are more affordable and readily available and just about any parts store. With that being said......I HAVE NO IDEA AS I AM NOT A MARINE OR AUTOMOTIVE MECHANIC. Heck I had to ask how to mount it....lol! I was going to mount it as you suggested but was worried about the current through it.....So the metal-to-metal is ok? Thanks!
 

Frank Acampora

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

The usual mounting in the auto was on the firewall. The resistors inside are insulated by the ceramic (and one is coated with an epoxy type substance) so there is no metal to metal contact or a possible short circuit
 

Chip Chester

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

BTW, take a look at the red rubber cap on the coil... it should seal nicely around the coil output connector. Is the one on the other end of the wire smaller? Might need turned around. It'll still run either way, but your connection will stay clean with the cap tight.

Chip
 

bankbuster

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

Hey Chip...I checked it out and the other end is inside dist. and the shop did it so noy sure what it looks like???? I just checked this side and all tight and sealed good. Thanks for the tip!
 

Frank Acampora

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

All wires passing into the distributor cap are seated in a thick rubber gasket. They go through the top of the cap, through the rubber gasket, and into seats in the lower portion of the cap. The seats have brass prongs inside that penetrate into the wire core. the upper cap is held to the lower cap with two screws and the two halves squeeze the rubber grommet. This effectively traps the wires and prevents them from pulling out. It also seals against water and gasoline vapors, making the cap corrosion resistant and explosion proof.
 

bankbuster

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

Hi Frank.....resistor is mounted. I'll check the cap/wires/seal tomorrow. Will post pic's as well.....I cant wait til the weekend! I hope to have a pic like yours as that says it al!
 

bankbuster

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Re: How and where to mount a ballast resister on a 1976 Chrysler 75hp model# 757HC

fixcars008.jpg
He it is mounted. i took the boat out. Ran great......for 15 minutes. Watch for new thread coming soon regarding melted boot on spark plug wires...???? Always something!
 
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