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  1. #1

    Default 1985 70hp Johnson - HELP !!

    just got this boat/motor. it ran poor from the start. loads of water
    in fuel seperator and did the following.

    - dumped old gas
    - replaced all fuel lines, from tank thru to carbs
    - cleaned and rebuilt all carbs, including new high & low speed jets
    - new spark plugs ( gapped correctly )
    - new spark plug wires
    - rebuilt fuel pump
    - replaced one of 3 coils
    - installed tach
    - compression check ( all with 10 of 110 )
    - checked timing, ( is it really just stop screws )

    got boat to start well, idle well, run well up to 4000 rpms then it bogs down.
    squirt pre mix into top carb at wot and motor would jump up to 5500 rpms.
    same story with holding in primer solenoid. jumps to 5500 rpms.

    - cleaned all 3 carbs again. this time soaked in mineral spirits for 20 mins
    and worked them with a toothbrush. blew them clean with compressed air.

    put it back together, started motor with muffs in driveway, a little hard to start but ran okay at idled to 2000 rpm for a good 10mins

    took boat to water, backed it in, lowered motor in water. motor would
    not start. waited 15 mins. shot some starting fluid into carbs, motor
    started. ran on trailer in water for 10 mins, then pushed her off
    and headed out. got up to 5500 rpms for about 30 secs, then she died.

    got it started again, and limped in at 1500-2000 rpms. lots of coughing,
    gasps and choking the entire way. anything over 2000 rpms she'd die.

    my current thinking is, fuel problems are now solved but there is now
    a spark problem. i have ordered a new powerpack and will install it
    and test again this friday.

    my question: - am i grasping for straws with the new powerpack, does it
    really seem like there is a spark issue, what else should i look for, consider,
    do or test ?

  2. #2
    Supreme Mariner
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    Default Re: 1985 70hp Johnson - HELP !!

    Personaly I'd only opt for changing (expensive) ignition parts if I was sure it had no spark. But only after I ran the tests to make sure I was replacing the correct component.

    If holding the primer in and / or squirting fuel into the carbs cures the issue I'd say you still have a fuel delivery problem. I'd start by soaking the carbs in carb cleaner. You say you installed new kits, we'll assume the floats are set correctly and are free. We'll also assume you didn't forget the round gasket over the emulsion tube.

    You mentioned the water separator, have you checked it again for water / debris? Also make sure you have the correct Champion plugs.

  3. #3
    Senior Chief Petty Officer
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    Default Re: 1985 70hp Johnson - HELP !!

    don't wish to appear harsh here but as dhadley has mentioned, if you hold on the choke or squirt fuel into the Carby it runs OK (well sort of) so why do you come to the conclusion there is a spark issue? not saying there isn't but just think about it for a second!

  4. #4

    Default Re: 1985 70hp Johnson - HELP !!

    seems like my post was not completely clear. there was a 2 step process.

    Step 1. Did everything listed, but soak and clean carbs with toothbrush.
    Results were, easy start, great idle, runs fine to 4000 rpm . wot bogs, squirt pre mix or hold primer solenoid jumps to 5500 rpm. obviously not the way
    she's supposed to run, so i keep trying.

    Step 2. Soaked and toothbrushed carbs, hit 5500 rpm WITHOUT squirt or primer push for 30 seconds. then died and ran worse then ever, poor idle,
    dies at anything above 2000 rpm, engine coughs, barfs, chokes, sputters.

    thinking is, fuel supply problem now solved but now have spark problem.

  5. #5
    Lieutenant Benny1963's Avatar
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    Default Re: 1985 70hp Johnson - HELP !!

    sounds like carbs still picking up trash any time you introduce external fuel to carb and it picks up it means that your not getting correct supply
    check your spark under load on trailer with timeing light
    when the prob occurs you will see the miss by looking into timeing light
    when you hit primer your motor should bog down not pick up sounds as if you have fuel prob run differnt tank and hose. bypass fuel filter if ya have one in line ,if that doesnt get it back off with the carbs pull welch plugs and jets
    soak overnight , blow with compressd air , i know you have had them down a couple of times but sounds like you have restriction in jetting.
    i pulled a carb five times with high speed bog finally took it to my boat guy
    i sonic cleaned it and used compressed air with small tip on it
    also had heavy float but that would cause over gassing on plugs what do your plugs look like
    Benny B

  6. #6
    Senior Chief Petty Officer
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    Default Re: 1985 70hp Johnson - HELP !!

    I'm not sure he tried squirting gas directly into it after it died after he cleaned the carbs, since he doesn't say he did.

  7. #7

    Default Re: 1985 70hp Johnson - HELP !!

    correct, i did not try squirting gas into carbs after it died.
    seemed pointless as the motor was just barley running.
    anything over 1500 rpms and she'd die.

    this behavior was brand new. before the soak it would
    run fine to 4000rpms then bog at wot.

    after the soak it ran for 30 secs at 5500 rpms then died
    and would only do 1500

    when it was running at 4000 rpms squirting only made
    a difference in carb #1, that's why I opened them up
    again and did the soak, thinking fuel starvation in #1

    after the soak since it got to 5500 rmps without squirting
    or primer switch on, i figured carbs are clean fuel problem
    solved. then 30 secs later it died and i limped in

  8. #8

    Default Re: 1985 70hp Johnson - HELP !!

    Well I got the new powerpack and put it in. Guess what same problems
    with a new twist. Now in addition to hard to start and running poor, I
    can't get it to idle at less then 2000rpms.

    So it seems my carbs or fuel supply are still bad. I got some berrymans
    and will soak overnight to see if that helps.

    The too fast idle has me stumped though. The butterflies on the carbs
    are closed and idle stop screw is not even touching the throttle arm/plate.

    Does anyone have some ideas to help me with the idle problem or/and
    thoughts about the carbs still not working right.

    Thanks, I eagerly await your replies....

  9. #9

    Default Re: 1985 70hp Johnson - HELP !!

    After more research I'm thinking the too fast idle
    is either a big air leak or the idle circuit in the
    new power pack is not working right.

    When I got the new pack, the connection
    pattern in one of the rubber boots did
    not match the old one. Attached is a pic.

    I doubled checked I had the correct pack then
    choose to swap the boots. I matched
    up the wires correctly and got it to plug
    in with no problems.

    Does anyone have some ideas for how
    to check the new power pack ?

    Thanks !
    Attached Images Attached Images

  10. #10

    Default Re: 1985 70hp Johnson - HELP !!

    Update !

    I fixed the fast idle problem, it was the power pack. One of
    the pins was bent a little in the rubber boot and not making
    a good connection. I also put three new spark plugs in
    and gapped them all to .035

    I got her running great with muffs, then took her to the
    water. She started fine and I took off, ran at WOT 5600 rpms
    for a minute or so.

    Then she bogged down, started to cough, sputter back fire,
    slog, choke, etc.... anything above 2500 rpms and she'd die.
    I tried some pre mix in the carbs during this and it made no
    difference.

    Anyone have a opinion ?

    It would be great to hear from someone with experience.
    This is my first boat and first time I've worked on a
    a motor since high school shop class 30 years ago.

    Thanks !

  11. #11
    Senior Chief Petty Officer
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    Default Re: 1985 70hp Johnson - HELP !!

    I am not a mechanic, but if spraying pre-mix in the carb did nothing I think you can rule out a fuel delivery problem. Sounds more like an electrical problem to me.
    If I'm wrong I am sure someone will correct me, and even if I'm right I am sure they will give more insight into what to check out and/or fix. I'm about as new to this as you.

  12. #12

    Default Re: 1985 70hp Johnson - HELP !!

    HybridMX6 - Thanks for the reply, I've been wondering if anyone has
    been reading my posts.

    I'm at the same conclusion you are, electrical. I'm thinking coil
    or rectifier or something else, just not sure which and how to
    test.

    Does anyone agree or disagree or have a comment about how to test
    or what else in the electrical area or elsewhere I should investigate.

    Thanks !!

  13. #13
    Senior Chief Petty Officer
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    Default Re: 1985 70hp Johnson - HELP !!

    Hello to you,
    Is it overheating on you, maybe that is why it runs at 2,500 RPMs after it heats up. If not get a hair dryer and warm the coils up one at a time and see if heat is causing the coil to go out and thus losing spark on bad coil. Check your spark plug wires and make sure there good also no cracks, detoriation, dry rot etc. Also make sure your coil grounds are clean and shiney as well as all the gronds on the motor, nice and shiney clean. Hope this helps you out somewhat without having to buy pars and put them in to find out it is another part and waste money. Let me know, Bob

  14. #14

    Default Re: 1985 70hp Johnson - HELP !!

    Bubba - No idea if it's over heating or not. There is no temp gauge
    so I have no idea about what the temp is. I don't even know where
    the thermostat on the engine is. Can you tell me where that would
    be located ? I'd like to inspect and see what it looks like.

    The spark plug wires are all brand new, I will check for shiney grounds
    plates on coils and the other grounds on the motor.

  15. #15
    Captain iwombat's Avatar
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    Default Re: 1985 70hp Johnson - HELP !!

    I haven't seen any mention of a spark check. Did you do one? What did it show?

  16. #16

    Default Re: 1985 70hp Johnson - HELP !!

    i've done spark check where I remove a wire and see if the
    engines acts differently, it does. i've also hooked up a timing
    light and got flash on all wires.

    if you are asking about the spark check where you test that jump
    thing, i've not done that yet. I don't know how to do it, what
    tools to use and what I'd be looking for.

    can you tell me if that's what you're asking and if so, how i do it
    and what it all means.

    thanks !

  17. #17
    Captain iwombat's Avatar
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    Default Re: 1985 70hp Johnson - HELP !!

    You should get spark to jump a 7/16" gap. You'll need to buy or make a spark tester. Plenty of info on that in the forum if you do a search.

    Spark test is the only real way to test for healthy spark.

  18. #18

    Default Re: 1985 70hp Johnson - HELP !!

    if the spark is bad, then what ? i've done wires, powerpack, new plugs
    and one of the coils.

  19. #19
    Captain iwombat's Avatar
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    Default Re: 1985 70hp Johnson - HELP !!

    If the spark is bad, then you start swapping coils, and testing components. If it's healthy you move on to the fuel issues.

  20. #20

    Default Re: 1985 70hp Johnson - HELP !!

    which components ?

  21. #21
    Captain iwombat's Avatar
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    Default Re: 1985 70hp Johnson - HELP !!

    Not to be too blunt about it, but I could sit here and type out pages of irrelevant test procedures all day.

    Lets see if the spark checks out, then on to what needs to get done.

  22. #22
    Cadet
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    Default Re: 1985 70hp Johnson - HELP !!

    i have a similar outboard (1990 60 HP) that had the same symptoms yours is having. Also: i did the same damned thing with replacing power pack, fuel delivery etc etc.

    MY problem was a crack in the lever of the primer solenoid. the problems was hard to catch because fuel would only leak under load and while powering up.. Just a thought of something else to peek at - I spend ALL THIS PAST SUMMER replacing electrical components, fuel delieveries, rebuilding carbs, etc etc.

  23. #23
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    Default Re: 1985 70hp Johnson - HELP !!

    I'd take an inductive timing light and a helper with you next time out on the water. When the engine starts to act up, check each of the 3 plug leads for spark. Check when the engine is under load. Hopefully, all 3 with show constant, rhythmic strong flashes. Look for intermittent or no fires. If you see problems, there are two other ignition components you have not mentioned checking, the stator and the timer base. Each can be checked electrically (with special tools and the service manual) and can contribute to the problems you mention. Electrical problems seem to show up once the engine reaches normal operating temps. All the ignition components are expensive, so a good upfront analysis is cheaper than just replacing components at random. I don't think the 85's had the SLOW system yet, so the pack should not be limiting revs to 2500.

  24. #24

    Default Re: 1985 70hp Johnson - HELP !!

    jblaiz - how did you find the crack in the primer solenoid ? i've had mine apart
    and nothing jumped out that was obvious. of course i was not looking
    for a crack... also, if i squirt pre-mix in the carbs and it makes no difference
    do you think it's safe to rule out fuel delivery ?


    emdsapmgr - beyond, power pack, coils, plugs, wires , " timer base & stator "
    are there any other components ? would a bad thermostat contribute to
    my symptoms ?

  25. #25
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    Default Re: 1985 70hp Johnson - HELP !!

    I doubt the thermostat is the cause of any of your problems, but a laser temperature gun would help determine if it is functioning propely. If the thermostat is stuck open, the engine will run cold. Cold running engines will smoke more and can accumulate carbon around the rings over a long period of time. If the thermostat is stuck closed, you will get an overheat horn at idle after just a few minutes. You did not mention any of these symptoms as being a problem.

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