1978 800 won't start

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hardwarejunky

Recruit
Joined
Jun 27, 2004
Messages
4
My "Project" is giving me fits. I recently acquired a 1978 runabout with the accompanying 1978 800 Mercury. All 4 Cylinders have constant compression of about 100 PSI. At this point no spark. I tested the stator and trigger per SELCO manual. Wires corroded replaced trigger. Tested spark and get spark on 1 and 2 none on 3 or 4. Where should I look next? I wouldn't think both 3 and 4 coils would be bad but want some advice before sinking more $$ into it. Any help would be greatly appreciated.
 
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: 1978 800 won't start

Hi, Jon.<br /><br />Welcome to iboats.<br /><br />Try swapping the 3&4 coils with the known good coils from 1&2. That should indicate whether they are good or bad.<br /><br />Good luck. :)
 
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Ben Konopacky

Petty Officer 1st Class
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Apr 5, 2004
Messages
296
Re: 1978 800 won't start

jon, try switching the #3 and #4 coil with #1 and #2 ( at the switch box )to see if you get spark on #3 and #4 if you do you know the coils are good,and if no spark on #1 and #2 then posable bad switch box .hope it helps . make shure all connections are clean and tight...
 
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andrewkafp

Lieutenant Commander
Joined
Mar 15, 2003
Messages
1,668
Re: 1978 800 won't start

You mentioned "Corroded" wires. Thoroughly check all the wires going to.. and and coming from the switchbox. A good way to test them is with a sharp probe at either end and a 1.5v battery and globe (cheap method) or a multi-tester with probes. They have a tendancy to look OK but may be broken inside. When 2 cyinders fail it is usually trigger/switchbox related. Silly question, but are the trigger wires connected in the right sequence?
 
H

hardwarejunky

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Jun 27, 2004
Messages
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Re: 1978 800 won't start

I swapped coil wires at switch box per suggestions and got spark on 2 but not 1. I switched back and switched red/green and red-white/green-white from stator to switch box. #2,#3, and #4 fire not #1. Would this be bad switch box, bad stator(wiring) or both?
 
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andrewkafp

Lieutenant Commander
Joined
Mar 15, 2003
Messages
1,668
Re: 1978 800 won't start

Go back to your Seloc and double check the wiring diagram for that motor. I can send you a good pic of my 1980 coilpack coil/Switchbox if you provide an e-mail.
 
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hardwarejunky

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Jun 27, 2004
Messages
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Re: 1978 800 won't start

Red-U --sent email to your profile email address. Reconfirmed wiring looks correct per Seloc.
 
H

hardwarejunky

Recruit
Joined
Jun 27, 2004
Messages
4
Re: 1978 800 won't start

I haven't been able to narrow down the problem, although I did test the rectifier and got continunity where Selco say's I shouldn't... Could this cause me to fire on only two cylinders?
 
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