OMC ESA head scratcher.

Craig S

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Aug 17, 2010
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I'm new here so hello everyone. This looks like an active forum so I thought I'd ask a question here.
I have a 1986 Avanti with an OMC 800 stringer mount powered by a 3.8L (229) GM engine. A little history: I had a lot of rot in the boat so I totally stripped it out and reinstalled a new transom, floor and stringers, then rebuilt the engine. In the process, I broke the overstroke switch off the shift control box. At the time I didn't know what it was for. Anyway I've been having frustrating problems with quick acceleration. (only in the water with the engine warmed up for a while) As soon as you threw the gas to it, it bogged. Well I went the carburetor route. I did my rebuild, no help, and then shelled out for a pro rebuild, no help. Then I started looking at ignition, points timing etc. Still no good. It's when I started looking for the ballast resistor (which I don't appear to have) that I started reading about the ESA and switches. Well the overstroke switch was broken in two but the contacts were still closed. ALL THE TIME. The button didn't matter. It was separated from the rest of the switch and contacts. I thought great, this means the ESA in on when I?m in gear. It makes sense. So I got a switch from Cherry (E72-40AT) mounted it to the arm and adjusted the stops. Well I got in the water and the ESA worked. The engine stumbled coming out of gear and smoothed out in neutral. It also stumbled going in gear and smoothed out just before throttle. So I got out of the cove and hit the throttle and it bogged again!! Finally I disconnected the ESA plug from the switches and presto, problem gone. Full throttle take offs all day without a hitch. Anyone seen this type of ESA failure before? It doesn't make sense.
I still have points and condenser in a prestolite distributor. (IBM 7021). My ESA module is a 982774 which matches up with a CDI 123-9898P. That could be my next step.
 

Howard Sterndrive

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Nov 5, 2008
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4,603
Re: OMC ESA head scratcher.

did you use the N.C., or the N.O. terminal of that Cherry switch?
Cherry-E72-40AT.gif
 

Craig S

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Aug 17, 2010
Messages
12
Re: OMC ESA head scratcher.

Thanks for the reply Howard. I used the normally closed contacts so that when I'm in gear, it hits the lobe and opens the circuit, disabling the module. I checked continuity at the plug and I had continuity moving out of neutral and the switch opens right before the throttle starts to open and stays open from there to full throttle.
 

Howard Sterndrive

Rear Admiral
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Nov 5, 2008
Messages
4,603
Re: OMC ESA head scratcher.

I agree you need a new ESA module then. The CDI one, although often used because it is electronic ignition compatible, will work fine with your points ignition. You should have an IBM7014 distributor, not 7021.

The 3.8 distributor is committed to points for life unfortunately - no electronic conversion for it
 

Craig S

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Joined
Aug 17, 2010
Messages
12
Re: OMC ESA head scratcher.

Thanks for the confirmation on my next course of action. I'll get one ordered and report back later with my success or failure. I sure wish I had a schematic and theory of operation for the guts of an ESA module. I understand what goes in and that the output to the coil causes the desired effect. How it all happens is a mystery.

It's ironic that you mentioned my distributor. I've already been researching electronic ignition, coil etc. I'll double check the distributor data plate. Who knows what was done by previous owner(s). I might start a new post when I get to that point.

Thanks again
 

d_carter

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Oct 7, 2009
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Re: OMC ESA head scratcher.

I have the same ibm 7021 distributor in a 4.3 and there is a prestolite kit for it. PN is 1563a
 

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: OMC ESA head scratcher.

I have the same ibm 7021 distributor in a 4.3 and there is a prestolite kit for it. PN is 1563a

he doesn't have a 4.3, he has a 3.8. He should NOT have a 7021 in a 229 Chevy. It will destroy the engine. The 229 is a semi even fire engine. The 4.3 is even fire.
there is no conversion for the 3.8
never was, never will be - it's points unless you want to use an automotive HEI unit (not safe)
 

Craig S

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Joined
Aug 17, 2010
Messages
12
Re: OMC ESA head scratcher.

While I'm waiting for my new ESA module to arrive, I'm going to start a new topic on this 3.8L and distributor issue.
 
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