install electronic ignition kit in a Mercruiser 120 engine?

[Neutron68]

Is it easy to install an electronic ignition kit in a 1978 Mercruiser 120 engine?
Just remove the points and condensor and install the electronic module?

[75starflight]

Correct, there are instructions in with the pertronix kits it is very simple and straight forward. I have one installed on my 120 and have not had any issues.

[Rich_V174SS]

I have one on my 3.7 liter, they're easy to install. Use a timing light to verify timing before and after installation because it may change a little once the Pertronix is installed. Also, it may work better to wire the positive lead of the Pertronix to a point in the ignition circuit before the ballast resistor instead of to the positive terminal of the coil otherwise you may lose power if you operate your trim while the engine is running.

[Neutron68]

I don't have a timing light.

What happens if it just swap the parts and make the prescribed connections as instructed, without adjusting the timing?

As I understand the electronic ignition kit, it fires based on magnetic sensor that senses the rotation of the distributor shaft.
Since the same shaft is used, won't the timing stay the same?

[Rich_V174SS]

As I understand the electronic ignition kit, it fires based on magnetic sensor that senses the rotation of the distributor shaft.
Since the same shaft is used, won't the timing stay the same?

Not necessarily. The point at which each pulse is sensed may be in a slightly different location from where the points arm gets lifted as it rides on the lobe of the cam, so you'd have to compensate for the difference by adjusting the timing. The difference, if any, is going to be slight but it's still a good idea to set the timing once the sensor is installed. If you don't check/set the timing then either your idle speed is going to be too fast or too slow depending on which direction the off-set is, and this also effects the wide open throttle timing which will either be too advanced or not advanced enough.

Points Ignition:


Electronic Conversion:

[Neutron68]

What do the red and black wires on the magnetic sensor connect to? 
If some new ignition module, does that come with the retrofit kits?

[Jerry]

I don't have a timing light.

Buy one!

[Rich_V174SS]

What do the red and black wires on the magnetic sensor connect to?

The black wire connects to the negative terminal of the ignition coil, just as the points have been connected to the coil. The red wire connects to a 12v+ source of the ignition circuit, most often the positive terminal of the ignition coil but I chose to connect mine to the terminal on the heater coil of the electric choke because that is a point in the ignition circuit that is before the coil's ballast resistor.

If some new ignition module, does that come with the retrofit kits?

Huh? 

[Neutron68]

The question got answered.

But to clarify, I was asking if the red and black wires connected to some new ignition module (not pictured)? 
And if so, did that additional module come with the retrofit kits?  Or would I have to also buy that box?

You see, I've been finding that there's often some addition thing you need to buy, when you buy a new boat part.
For example, you can buy a brand new aluminum propeller for around $120, BUT you need to buy a $50 adpater kit in order to use the new prop with your 1978 drive!
See what I'm getting at?

[Rich_V174SS]

Yes, I understand.   

With the Pertronix no additional hardware or modules are needed, it comes with all that is required.

[Jason]

If your points still work fine leave it alone. I had problems with Petronics.

[Rich_V174SS]

If your points still work fine leave it alone. I had problems with Petronics.

Like what? I've had no problems with mine.

[75starflight]

Me either and sold hundreds of them at work without issue.

[Neutron68]

The reason I'm thinking of replacing the old points system is becuase the repair shop that just refurbished the lower unit and drive unit said the points were burned and the condenser was rusty.  There is mounting evidence that one of the previous owners let water condence in various parts of the engine.  The marine shop (just north of Cold Spring, MN) advised replacing the distributor cap, points, condenser, spark plug wires and spark plugs.  I didn't have them do that work because they quoted parts and labor at $291 for all that.  My thought is that if they need replacing, I don't want to replace them with the old technology that will require replacing and gapping again and again.  I want to do this once and never again.

For reference, the last car my family had with pionts in it was a 1974 Suburu and we sold it in 1981.  I haven't seen points since then!

Eric

[Rich_V174SS]

Ever since I installed one on my engine the timing has been rock solid, no wavering, and I don't have to worry about changing points and condenser anymore. To me it's much more reliable.

[75starflight]

Ever since I installed one on my engine the timing has been rock solid, no wavering, and I don't have to worry about changing points and condenser anymore. To me it's much more reliable.

Same here, no replacing parts, and starts better IMO.

[Neutron68]

Ever since I installed one on my engine the timing has been rock solid, no wavering, and I don't have to worry about changing points and condenser anymore. To me it's much more reliable.

That's awesome.  I look forward to similar performance.

Are all the kits the same?  Should any brand be avoided?

Eric

Eric

[75starflight]

Pertronix is the original that all are based off of. As long as they have some sort of warranty you should be fine. EBay and amazon are the best two places to find them for a good price.

[MarkS]

Many of the auto parts stores around here have a tool loan or rent program, put down a small deposit you get back when you return the tool (timing light).  Might be an option, you probably won't need it again after you get the Pertronix kit dialed in?

[Neutron68]

What Pertronix part number do I need for a 1978 Mercruiser 120 (4 cyl.)?

iboats.com lists a number for Sierra and Mallory, but not Pertronix

Is it a Pertronix 1146A?
http://www.go2marine.com/product/90148F/electronic-ignition-conversion-kit-delco-4-cyl-1146a.html