1971 Johnson 4hp no spark / possible bad coils?

SusieQ 21

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Motor rescued from my barn after 50 year retirement. Bought it new and only used in fresh water a few times back in the 70’s. Ran great back then. Still looks almost new. After oiling cylinders, I pulled it a few times but had no spark. Removed flywheel and cleaned / checked point gaps. Points looked good. Installed new plugs. Still no spark. Although manual states that coils can ONLY be tested with engine running, I opted to remove coils and check for grounding and resistance. Both coils tested at 1 ohm. Not certain what resistance should be present, but at least there was continuity. Because of age, I presume coils may be bad, although I saw no external cracking (see attached pics). Before I order new replacement coils, would appreciate any comments / suggestions.
 

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Crosbyman

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coils look.. ok primary wire ( between short ones) at 1 ohm is OK from either short wire to the spring in the boot end should read 4-8 KILO ohm on the proper scale.

condensers likely gone bad (small investment) . basic testing for capacitance kicks does not mean much... dead short 0 ohms is bad....
any steady resistance is bad.. meter must swing to infinity

points must be clean clean clean !!! at .020 openning on the high point of the cam.

mag plate looks messy with frayed wire clippings, lint ?? one point seems to have a piece of paper or felt across the point.

keep all coil point wires away from the rotating shaft !!

put 2 drop of oil on the felt to lubricate ( I use GC oil... 1-2 drops) no more !
 

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racerone

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Replace condensers.----Clean and set points.----Spark should return.
 

SusieQ 21

Seaman
Joined
Jan 5, 2022
Messages
54
coils look.. ok primary wire ( between short ones) at 1 ohm is OK from either short wire to the spring in the boot end should read 4-8 KILO ohm on the proper scale.

condensers likely gone bad (small investment) . basic testing for capacitance kicks does not mean much... dead short 0 ohms is bad....
any steady resistance is bad.. meter must swing to infinity

points must be clean clean clean !!! at .020 openning on the high point of the cam.

mag plate looks messy with frayed wire clippings, lint ?? one point seems to have a piece of paper or felt across the point.

keep all coil point wires away from the rotating shaft !!

put 2 drop of oil on the felt to lubricate ( I use GC oil... 1-2 drops) no more !
Crosbyman and Racerone, Thanks for your responses and advice.

I ordered new condensers today. Didn’t bother with testing, other than to see if there was continuity between the case of the condenser and the wire connector. It measured 0 ohms, so assumed a dead short. Not certain if that’s a legitimate test, but doubt there should be continuity, as indicated by your explanation. Must admit, didn’t know condensers have a shelf life. Although it was always automatically a part of points replacements in my old cars, I always thought it was more of a preemptive maintenance measure against sudden failure (which it was), but not necessarily a result of internal packing age degradation.

Checked points again. I didn’t see any paper between either contact set. There was a small piece of lint left on the plate from a cleaning rag. Gaps were precisely at .020" with no pitting. I cleaned both sets again with alcohol, and followed with a piece of folded paper to carefully pull through closed contacts. It came through clean on both sets.

Regarding observation of wire clippings, I’m not certain what or where they were seen. I went back over everything and couldn’t find anything. That said, I don’t doubt you saw something. I say that, since I must admit to a huge screw-up while testing for spark. After initial cleaning and checking point gaps, resulting in no spark, I thought by increasing the cranking speed, it might be more likely to achieve a spark. That said, I attached an impact wrench to increase starting RPM and produce voltage. In the process I stripped the flywheel nut. Fortunately, I didn’t damage the threads on the crankshaft, but the attempt left some fine threads from the nut on the shaft. So, when I removed the threads, a few strands may have escaped. I have since made certain no remnants remain. VERY, VERY embarrassing!

I will repost anticipated success when I receive / install the new condensers. Again, many, many thanks.
 

racerone

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I can
't believe that someone would use an impact wrench to spin over that 4 HP motor!!--A magneto in good condition will produce a strong spark with the recoil or rope wrapped around flywheel.
 
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Crosbyman

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hopefully tou tested condensers stand alone (not connected) otherwise that short was a measurement from grd to grd !! thus 0 ohms
 

SusieQ 21

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I can;
't believe that someone would use an impact wrench to spin over that 4 HP motor!!--A magneto in good condition will produce a strong spark with the recoil or rope wrapped around flywheel.
Yeh, well I stand corrected. First outboard I have ever worked on, hopefully my last. Still learning, but no excuse, I guess. Just being honest.
So, have you ever made a mistake….and admitted it? Maybe you could share a couple of those with us.
Regardless, thanks for the lesson.
 

racerone

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Made a lot of mistakes in school years ago.----Teachers corrected me.----Deducted marks.----And I did not get mad amount it.----Folks today are different.
 

SusieQ 21

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hopefully tou tested condensers stand alone (not connected) otherwise that short was a measurement from grd to grd !! thus 0 ohms
Promised to post results. New condensers solved the spark issue. Many thanks for your help and constructive responses. Happy Holidays!
 

Crosbyman

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glad you solved it... those 4 hp ( I have three refurbished) are great litlle kickers for trolling and back-ups to modern fussy engines.

a great book to help out from the past ..it does not cover your 4hp1971 but.... for 20$ it is a great read on general maintenance of oldies like the JW 3hps ... most of those small oldies use similar parts coils condensers points etc.. on the magnetos. and carb parts :)

 

SusieQ 21

Seaman
Joined
Jan 5, 2022
Messages
54
glad you solved it... those 4 hp ( I have three refurbished) are great litlle kickers for trolling and back-ups to modern fussy engines.

a great book to help out from the past ..it does not cover your 4hp1971 but.... for 20$ it is a great read on general maintenance of oldies like the JW 3hps ... most of those small oldies use similar parts coils condensers points etc.. on the magnetos. and carb parts :)

Many thanks for your reference to the manuals. I sure intend to order one. Although the 4 hp, is too small for my (21’) boat, if it proves to be reliable, I’ll be looking for a small Jon boat to fish the shallows.

FYI, I haven’t attempted starting yet. I need to mix some fuel and check for leaks, as well as locate a suitable tub for water. Of course, if/when it starts, I will replace the water pump (impeller) and change gear oil. After 50 years of storage, I’m guessing I’ll find a few leaks and/or a gummed carb, etc. Regardless of discoveries, I’m optimistic any needed repairs should be relatively easy to diagnose and/or repair, even considering my novice experience. Parts seems to be available for my model. Seems ignition system diagnosis is my nemesis; so, I sure appreciate your direction with the points/condensers.

As mentioned in earlier posts, other than minor maintenance and repair on lawn mowers / lawn equipment and small displacement motorcycle engines, I’m new to, or at least inexperienced with, 2-cycle engines. Consequently, I sincerely appreciate your patience and sharing of your experience and knowledge. I’ve sadly discovered, not all contributors demonstrate equally benevolent intent. Thanks again…..and happy holidays!
 

Crosbyman

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Happy Holidays to you to ! the 4hp is a great learner engine. In a tub don't run it to fast because the prop generates lots of air bubbles and impeeds cooling after a while. replace oils and impeller before testing.

it should spit water out

look up utubes lots of them... here is one :)
 
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SusieQ 21

Seaman
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Jan 5, 2022
Messages
54
Happy Holidays to you to ! the 4hp is a great learner engine. In a tub don't run it to fast because the prop generates lots of air bubbles and impeeds cooling after a while. replace oils and impeller before testing.

it should spit water out

look up utubes lots of them... here is one :)
Thanks for the tips. The video was interesting. It mentioned a link for increasing horsepower on the 4 hp, but I didn’t see it. Curious how that is done, although I’ll be content with reliable performance if the stock 4hp. Thanks again.
 
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