Weak spark on 1973 20 Hp Johnson

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    fleetwin

    US Member - 2 Years
    Replies: 3278
    Topics: 49
    #209280

    All I know of this system is what you, fleetwin, and some others have so nicely and thoroughly explained. So I’m learning as I go. I see what Phil says about the flywheel on these having 2 magnets. I looked at the flywheel from my 1973 Evinrude 25 HP that came with the low tension magneto and noticed that. I’m not trying to confuse the issue or say it should be run like this, but just wondering if that setup with the 2 driver coils would work with the earlier flywheel with just one magnet? Maybe that’s how the seller used it?

    Not saying that this addresses the weak spark issue, just throwing a couple thoughts out there.

    Also, as a side question, why did OMC go to this system in the first place? Was it just an attempt to move the coils out from under the flywheel so they could be replaced easier?

    73E25-flywheel

    • This reply was modified 2 weeks ago by Steve DSteve D.
    • This reply was modified 2 weeks ago by Steve DSteve D.

    Well Steve, anything is possible. I guess we will see what happens when he tries out this crazy set up. Your flywheel theory might be the answer, unfortunately E-25 doesn’t have one of each style flywheel to try.
    This system was the intermediate stop between regular magneto ignition and CDII, which was introduced in 1977. One of the reasons this system was introduced was to make room for alternator windings under the flywheel…Deleting one of the coils under the flywheel made room for the alternator windings. The low tension mag plates on the 9.9-15, 35, and 40hp models had bosses to accomodate an alternator winding. The 22CI engines used the regular universal mag plate, so the alternator windings would not bolt up on these engines. Don’t know why OMC didn’t leave the universal mag set up in place on the 22CI engines until 1977 though.

    Steve D
    Steve D


    Replies: 572
    Topics: 67
    #209303

    Lot more to it than I realized. Thanks for expanding on it with all that good extra info.

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    fleetwin

    US Member - 2 Years
    Replies: 3278
    Topics: 49
    #209321

    All of this is great for me also Steve, a good review of this system is always helpful to me. I can’t wait to see what happens with that crazy mag plate installed. Part of me hopes that it does work, so we can figure out how and why it works….

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    Evinrude 25


    Replies: 12
    Topics: 4
    #209337

    The picture is the back of the magplate (2 coil setup) that I am going to purchase from EBAY. It is definitely for Canadian market since the seller located in Canada and he parts out his outboard. My current flywheel has two magnet (the same picture from Steve D). So when the flywheel rotate 180, it will generate the charge for both coils and both spark plug fired at the same time???
    Base on all the discussions, I hesitate to try this system. I rather stay with original OMC design (1 Driven Coil) so I order the NOS OMC EVINRUDE JOHNSON coil assy 581130 (picture) for $22 and know that I have all completely new (Point, Condenser, Driven Coil and two Charge coils).

    581130

    • This reply was modified 1 week, 5 days ago by MumblesMumbles.
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    fleetwin

    US Member - 2 Years
    Replies: 3278
    Topics: 49
    #209356

    How much does he want for the mag plate? I would buy it anyway if it is reasonbly priced… True, you will probably end up staying with the original system, but having the extra pieces is always good… Especially if the mag plate pilot bushing is in great shape… Two extra driver coils, and the all important primary wiring harness….
    Would you mind sharing the ebay link with us? I promise not to buy it..
    OK, so it seems like you are going to buy it, good… Once it arrives, please take detailed pictures of how the driver coils are connected to the points…Like I say, either the two driver coils are connected in series, with one end of each connected to a set of points. Or, one leg of each driver coil is grounded… If you can, ask the seller if his flywheel has one or two magnets…
    It will only take a few moments to just install that mag plate the way it is to see if it sparks. Let us know….

    • This reply was modified 1 week, 6 days ago by Avatarfleetwin.
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    fleetwin

    US Member - 2 Years
    Replies: 3278
    Topics: 49
    #209358

    OK, found the ebay auction….He wants big money for that piece…You may want to reconsider buying it…

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    Evinrude 25


    Replies: 12
    Topics: 4
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    fleetwin

    US Member - 2 Years
    Replies: 3278
    Topics: 49
    #209425

    Just emailed the seller and asked for more specifics about this set up….Will let you know what he has to say….

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    fleetwin

    US Member - 2 Years
    Replies: 3278
    Topics: 49
    #209442

    OK, seller replied. He said that the other driver coil is not used for ignition purposes…It is for a AC lighting coil, which makes some sense. Plus, I can see the two terminal ends from this coil coming out of the wiring harness…I am used to see only double wound alternator windings or AC lighting coils, but this mag plate would not accept that piece. So, this was some sort of accessory for overseas engines….
    Makes sense now, I just assumed that other coil was used for ignition….
    But again, this item seems a bit over priced…Unless it is in absolutely perfect condition….

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    Evinrude 25


    Replies: 12
    Topics: 4
    #209535

    Is it possible to gain 5 hp more when installs a 25 hp carburetor on 20 Hp? I saw a 25 hp carb on sale “JOHNSON EVINRUDE 25 HP 385815 CARBURETOR 1973 TO 1976 YEARS GOOD CORE 2 REBUILD”. It is interesting to know if it is just simply swap the Carb or more things involved to get additional 5 Hp.

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    fleetwin

    US Member - 2 Years
    Replies: 3278
    Topics: 49
    #209652

    Sometimes these engine have an intake manifold with a restricted/small diameter inlet. Installing the larger throat 25hp carb might not work out very well…Not saying it won’t work, but you should have a look at the intake manifold and carburetor throat first. It’s not always as simple as the seller claims… How much does he want for this “core”? I wouldn’t pay too much for it, consider it a gamble that might not work out.
    I would get the engine running properly with its original carburetor first before attempting to swap out the carbs…

    phil
    phil

    US Member - 2 Years
    Replies: 140
    Topics: 18
    #209673

    The 25hp 22ci engines had a number of changes other than the carb. I seem to recall they include (at least):

    Balanced crank
    Piston pin location changed (for porting and/or compression)
    Different cylinder head
    Exhaust tuning

    And maybe also improvements in the lower unit (gear case)

    http://www.omc-boats.org
    http://www.aerocraft-boats.org

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    Evinrude 25


    Replies: 12
    Topics: 4
    #210239

    Hello All,
    Her is the update the status of my 20 Hp Johnson:
    1) Compression: 114/112 psi
    2) Have spark on both cylinder. With the help of this forum, I will be able to get the spark of both cylinders. The update of the hardware: two new Mallory Marine Ignition Coil 9-23106, OMC OEM Outboard Tune Up Kit 172523, The driver coil (old) is still there even though I bought (OMC COIL #581130) but did not install yet. I did timing of the point based on the you tube that use ohm meter. So far I got good spark!
    3) Clean the old carburetor and put it in, I could get it run for but it is hard to get it running but whenever it runs it runs good. Note: the Carb is not in good shape. I have 3 spare Carb from 1981 70 hp Johnson. By the look they are the same as 20 hp carb. I could take one of them and try out. There are a couple external hardware different and the butterfly plate which I could swap them out to match.
    What do you think?

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    fleetwin

    US Member - 2 Years
    Replies: 3278
    Topics: 49
    #210242

    First, please don’t every try to swap throttle or choke shaft components by removing the butterflies. The butterflies are staked in place for a good reason, you sure wouldn’t want the screws to get sucked out and gobbled up in the powerhead….Plus, the butterfly could get jammed in the WOT position, usually at the most dangerous moment.
    What I’m hearing you say is that your engine is hard starting when cold, but once warmed up it starts fine, do I have it right?
    If so, I would have a look at the choke linkage, some of these designs are not the greatest…Some of the chokes rely on the choke knob bushing to hold the choke completely closed….So, I would have an assistant pull the recoil while you ensure the choke is completely closed.
    The carbs from the 1981 70hp will not work on your 20hp….Completely different design, even though it might “bolt up” OK.

    Avatar
    Evinrude 25


    Replies: 12
    Topics: 4
    #210276

    Yes, initially it was hard to start, 10-20 pulls to get it run but when it ran, I could start again with a couple pulls. The idler needle sets out 2 turns from fully seated some time I had to back out 1 more turn to make it run. Ok I heard from you to give up using 1981 carb. I will order the carb kit and rebuild it. I may redo the cleaning again when the new kit coming. The choke linkage was not a clean design!
    Note: the bottom part of the 1973 Carb is the same part number of 1981 carb.

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