Electronic Ignition Upgrade to Mercruiser 170

[TBB]

Hi, I've got a 1986 Mercruiser 170 (3.7L) with the Delco distributor. I bought a Perktronix "Ignitor" to replace my breaker points. My question has to do with the wiring of the Ignitor and whether or not I have a "ballast resistor". Note that the coil is a Mercruiser coil without an internal resistor -- says external resistor on the side.

Right now, I've got the red wire from the Ignitor connected to the (+) side of the coil. Also connected to the coil (+) side are a purple/yellow striped wire from the starter slave solenoid and a solid purple wire from the choke. The solid purple wire is labeled as a "resistance wire" in the wiring diagram for the engine.

Is the "resistance wire" the same thing as a "ballast resistor"? If so, where should the red wire from the ignitor be connected -- at the coil (+) or upstream of this so-called resistance wire?

What is the function of the ballast resistor? Would I be better off with a different type of coil for electronic ignition?

Thanks.

 

[Fishermark]

Re: Electronic Ignition Upgrade to Mercruiser 170

Remove / bypass the resistor wire (yes it is the same as a ballast resistor). Put a different coil on it with an internal resistor, and then provide it with a full 12volts switched power.

 

[TBB]

Re: Electronic Ignition Upgrade to Mercruiser 170

What is the risk if I just leave the old coil and resistor wire connected, with the ignitor red wire connected directly to the (+) side of the coil?

Suggestions for a coil upgrade that is marine compatible (not an oil filled coil)?

 

[Maclin]

Re: Electronic Ignition Upgrade to Mercruiser 170

The Pertronix unit needs to be connected to a full 12 volt supply. The coil positive terminal only gets 9-10 due to the ballast resistance.

 

[danond]

Re: Electronic Ignition Upgrade to Mercruiser 170

The Pertronix kit came with a full set of very descriptive instructions. You might try to find them.

 

[TBB]

Re: Electronic Ignition Upgrade to Mercruiser 170

Thanks all for the suggestions. I'm going to buy a matching Pertronix Flamethrower coil (epoxy) with 3 ohms of internal resistance to replace stock coil so I can go with a full 12 V. How do I remove the ballast resistor without disabling something else?

A purple wire goes from the ignition switch to the choke. A second purple wire piggybacks from the choke to the (+) side of the coil. The wiring diagram describes this second wire as a "resistance wire". I measure the voltage at the coil at about 8 volts. Is this truly a special wire that provides the resistance to lower the voltage at the coil? If so, it would seem that all I need to do is replace this wire between the choke and the coil with a "conventional" wire and I will have 12 V at the coil.

Thoughts appreciated, thanks.

1986 Searay Seville Cuddy - Mercruiser 170

 

[Maclin]

Re: Electronic Ignition Upgrade to Mercruiser 170

Did you measure voltage at the choke + terminal? If it has 12v then that sounds correct to me.

 

[Fishermark]

Re: Electronic Ignition Upgrade to Mercruiser 170

How do I remove the ballast resistor without disabling something else?

Simply disconnecting the wire at the coil works fine, it will not affect anything else.

it would seem that all I need to do is replace this wire between the choke and the coil with a "conventional" wire and I will have 12 V at the coil.

Yep.

 

[tsr966]

Re: Electronic Ignition Upgrade to Mercruiser 170

How was your boat running before and after the pertronix?