Prestolite Distributor on '94 4.3 OMC

[bradjarnagin]

Hello all, new to the forum. 2....yes, 2 years ago, my distributor on my boat went out. Kept having to adjust timing to keep it running, took cap off and the guts had virtually disintegrated. Couldn't find a direct replacement so I went with a $500 Mallory distributor thinking my problems were solved. Wrong. It ran better with my old distributor. It would at least run, it just jumped time. This Mallory is horrible. My friends and I fought it every spare minute we had last summer and never got it to run right. For some reason the Mallory does not seem to be compatible with the engine. I've triple checked the wiring diagram and had several other people check it as well. Changed plugs, wires, coil, as well as the external resistor. It runs great until it gets hot, then it starts missing and cutting out. It usually won't flat out die, but it don't have enough power to plane off. It will run 45 MPH while going out and about 15MPH coming back in. I've looked off and on for 2 years for a direct replacement for the Prestolite Distributor to no avail. Any ideas? Because I'm all out of them. The Prestolite tag looks like this:
98685
Prestolite
IDU 7602A 5 D

Please, someone, anyone....HELP! I'm Desperate! 2 years is too long to not have my boat on the water! Thanks guys, Brad.

 

[bruceb58]

Re: Prestolite Distributor on '94 4.3 OMC

Is this Mallory distributor a points distributor? If it's not, why do you have an external resistor? What does the manual for the Mallory distributor tell you to use?

What is the model number of your OMC? The reason I ask is that this is the year that OMC did the joint venture. If you have the older dog clutch OMC, you should unplug the ESA module and see how it runs. I would also try disconnecting the tach too.

If you have the newer drive, i would just replace the distributor with the Delco EST. Even with the older drive you may be able to use the Delco distributor with a CDI ESA. If you have the older Cobra drive, i would be very surprised if your current ESA even works.

This is of course all betting that its the ignition that is your problem.

 

[Walt T]

Re: Prestolite Distributor on '94 4.3 OMC

Triple check the firing order. Does the timing change by itself? If so it's timing chain or cam gear. However the only time I ever saw a cam gear problem was a frozen engine with a cracked valley that bent the camshaft. The customer never bothered to tell me about the frozen engine he drained all the water out of when he changed the oil. My first hint was water literally filling the bilge from numerous cracks. The idiot knew. He said the bilge pump should be able to keep up so he just wanted it to run right. I am not making this up.

 

[bradjarnagin]

Re: Prestolite Distributor on '94 4.3 OMC

Not sure on the OMC model number. Will have to look after work this evening. The Mallory is an electronic distributor. I ran it without a resistor initially and someone told me I probably needed one. The directions to the Mallory also seemed to indicate that it needed a resistor also. The factory distributor had broken pieces under the module, it also Had a missing spring. I assumed that's why it was jumping time. I will reply more thoroughly when I get a chance to investigate more thoroughly this evening. Thanks for the replies.

 

[bradjarnagin]

Re: Prestolite Distributor on '94 4.3 OMC

Found a model number on the right side valve cover. The top model no says 987344. There's also another model no underneath that that says 432APRJUN. And here's the Mallory that has been installed. CHEV V6 4.3L MBI MARINE - DIST The reason I have always believed it to be an ignition issue is because it ran great other than jumping time with the old distributor. Once I installed the new Mallory is when all of my problems began. I am already $500 in and don't want to throw in the towel on that kind of $. All advice is appreciated! Thanks guys.

 

[bruceb58]

Re: Prestolite Distributor on '94 4.3 OMC

yes, looks like they want you to have the resistor. What is interesting is that they show to diagrams, one shows the distributor picking off 12V before a ballast resistor and the other picking it up after a loom resistor. How do you have yours hooked up?

Out of curiosity, does your ESA work? From your model number of your OMC, you have the dog clutch version which is actually a 1993 model. Your model number is probably actually 432APRJVN.

 

[bradjarnagin]

Re: Prestolite Distributor on '94 4.3 OMC

This is my first inboard ever so forgive my ignorance but I have no idea what the ESA is or does. I've mainly worked on Chevy cars all my life, not boats. Which is pretty much killing me now! I'm pretty sure that I have the ballast resistor inline between the coil and distributor on the + side.

 

[MikDee]

Re: Prestolite Distributor on '94 4.3 OMC

OMC - Electronic Shift Advance, it kills spark to 1/2 the engine to make it easier to shift through the gears. Taking stress off the gearcase.

 

[bruceb58]

Re: Prestolite Distributor on '94 4.3 OMC

The ESA allows you to shift OUT of gear when you are in the water. It should not operate going into gear or when you run the drive on muffs.

 

[Maclin]

Re: Prestolite Distributor on '94 4.3 OMC

The engine has no preference regarding how the spark is delivered, only that it be delivered in sufficient quantity and quality and at the right time. In my opinion any perceived incompatibility would be in the (possibly incorrect) wiring and other components in that circuitry.

 

[bradjarnagin]

Re: Prestolite Distributor on '94 4.3 OMC

Thanks for all of your feedback, I haven't had time to do anything with it, been working too much. I am going to hop on it this weekend if the weather permits and see where we're at. I'll let you guys know. Once again, thanks a lot! I'm dying to get back on the water!