Installing EST Distributor on 3.0L Mercruiser- Some questions

[Darren J]

Replacing my points distributor with a complete EST system on my 89 3.0L merc. Install is fairly straightforward except for one area I'm trying to understand.

The EST dist. requires a black wire to be hooked up to my shift interrupt switch. Is the original function of the interrupt to ground the coil, stopping spark or does it cut off power to the coil? I'm not sure what the EST dist. requires in this area. I don't see the wiring diagram for the EST in my service manual.

 

[Don S]

Re: Installing EST Distributor on 3.0L Mercruiser- Some questions

Not sure which black wire you are referring to, it may be from the EST distributor kit, and without seeing your instructions or kit, it's hard to say where it goes.
Here is some EST information for the 3.0L with wiring diagrams showing where things should be hooked. Mercruiser has been using the EST for many years.

View attachment 3.0 EST timing.pdf

 

[Darren J]

Re: Installing EST Distributor on 3.0L Mercruiser- Some questions

Thanks for the diagram, I think I understand it better now.

On the EST distributor shown in your diagram there's a wht/grn wire leading from the distributor to the shift cut-out switch. That's the one that I'm talking about. 2 plugs are supplied to me in the kit. One with the jumper already installed, and a black single lead that has to be attached to 12V, which is used to set base timing and another plug with a single black wire which is installed after the timing is set. I think the single wire requires 12v to be sent through the shift cut-out, that must tell the distributor to stop sending spark to allow shifting.

The current configuration on my points distributor (I think) is that the cut-out sends the (-) side of the coil to ground, stopping spark momentarily to allow the shift ?

So I just have to wire the cut-out as per the EST diagram I guess.

 

[Don S]

Re: Installing EST Distributor on 3.0L Mercruiser- Some questions

Below is the wiring diagram of your old system. Not that the black wire from the shift interrupt goes to ground, with your EST distributor, you will want that black shift interrupt switch to go to a purple wire which is ignition, then the green white wire will go to the distributor.

View attachment #13 GM 4 cyl 90-97 253.pdf

 

[TurboM700]

Re: Installing EST Distributor on 3.0L Mercruiser- Some questions

Is there a kit for this Dist. or are you just pulling it out of an old boat. This is something I would like to do.

 

[Don S]

Re: Installing EST Distributor on 3.0L Mercruiser- Some questions

Several places make kits for them. Just google EST distributor kits.

 

[Darren J]

Re: Installing EST Distributor on 3.0L Mercruiser- Some questions

Perfect, know what I have to do now. Thanks.

TurboM700, I got mine from michiganmotorz. It is a full retrofit kit, distributor, coil, plug wires, terminal plugs, even includes the distributor hold-down clamp and bolts. All you need to do is figure out the wiring and have some spare wire and crimp terminals. My points distributor system needed a lot of new parts, the cost benefit was definitely there for the new one.

BTW, don't accidentally recycle bin the instructions like I did. Makes it a bit harder...

 

[kd7isf]

Re: Installing EST Distributor on 3.0L Mercruiser- Some questions

Call or e-mail michigan motorz... Those guys are really helpful -- they will probably just e-mail you a new copy of the instructions..

 

[Darren J]

Re: Installing EST Distributor on 3.0L Mercruiser- Some questions

Got the distributor installed and engine is running smoothly. Used the jumper plug to set base timing and I rewired the shift cut-out to apply 12v to the distributor as seen in the factory wiring diagrams. Tidied everything up with some wire loom and it almost looks like a factory install. Couldn't be happier.