Sears 3hp intermittent Spark

eg30.06

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Joined
Apr 23, 2017
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5
Hey all, have a old 73 Sears 3 horse outboard with intermittent spark. I replaced the coil, condenser, plug, cleaned tank and carb, cleaned and set pints and cleaned all connections with no success. Any ideas? Will kinda run but dies off full throttle. I believe I set the points correctly at .020 off the top of the cam.
 

robert graham

Admiral
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Apr 16, 2009
Messages
6,908
If it runs good and dies at full throttle maybe it's a fuel delivery/venting problem....I've been running a Sears/Tanaka 3HP since 1983 and never an electrical issue....only fuel flow/venting problems. That little petcock can restrict flow...replaced mine with a small plastic chain saw type unit...
 

eg30.06

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Joined
Apr 23, 2017
Messages
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If it runs good and dies at full throttle maybe it's a fuel delivery/venting problem....I've been running a Sears/Tanaka 3HP since 1983 and never an electrical issue....only fuel flow/venting problems. That little petcock can restrict flow...replaced mine with a small plastic chain saw type unit...

Thanks for the info. After further testing I found that when pulling over with a spark tester it will have spark on one pull and then none on the next and so on. I think I set the points rite. Set to .020 at the steepest point of the lobe.
 

brim_buster

Lieutenant Junior Grade
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Jul 9, 2013
Messages
1,203
breaker point gap is .018 to .020 depending on powerhead and spark gap is .030 and J13Y champion plug fuel mix is 24:1 for motors till 73 and 32:1 after 74
 

eg30.06

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Apr 23, 2017
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I rechecked everything from gaps to connections and all seems good. I thinking I might have gotten a bad new coil or condenser???? Im pretty positive I have a spark issue as when i can get it to run it runs as though someone was grounding out the plug every other second as the rpms will rise the fall.
 

gm280

Supreme Mariner
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Jun 26, 2011
Messages
14,585
If you changed the coil, do you still have the old one? If so try it and verify your thinking. JMHO
 

eg30.06

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Apr 23, 2017
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Just swapped out to the old coil and got nothing. No spark. Put the new coil back in and there's spark but it's so dull you can hardly see it on the test light.
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
Just swapped out to the old coil and got nothing. No spark. Put the new coil back in and there's spark but it's so dull you can hardly see it on the test light.

Well it sound like you have locate a possible defective coil. I would buy another and install. Either way you will know if the coil was the problem. And if it doesn't fix the issue, you also then know the problem isn't the coil and you then have a spare. I hope the coils aren't too expensive.

If you have an ohm meter, you could even ohm out the coil to see what it is reading. I hate buying parts to try and fix things without verification that is the problem first. But unless you have the proper test equipment, you don't have any other option.

If you are very creative, you could makeshift another coil in its place and see how that works. It won't be the exact replacement obviously, but could confirm the defective part. Just an idea. JMHO
 

tomhath

Master Chief Petty Officer
Joined
Dec 5, 2007
Messages
814
I have the same motor, fiddled with the ignition several times before I got a good spark. What did it for me was very careful cleaning of the points and checking with a meter after setting them to be sure the connection was perfect. Just the tiniest bit of lint will cause a weak spark. Also make sure the coil is as close to the flywheel as you can get it without rubbing.
 
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