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  1. #1

    Default 1978 85Hp Johnson is hard to start cold, easy when hot.

    Help please I’ve rebuilt the carbs so I feel like they should not be my problem. I’m following the general cold starting procedure others find works but I’m having to wind it over many times to finally get running. The fuel primer bulb stays hard for some time if I pump it so I don’t think I have any bad fuel leaks. The age of the plugs is unknown. I pulled the fuel line off and tested the pump it seems to be pushing fuel ok. This motor only has about 100-105 psi on all cylinders which I know is low but it wasn’t as difficult to start on our first run and had that compression then too. It has an electric choke which appears to be working.

    The reason I rebuilt the carbs was the motor was prone to flooding easily.
    Once it’s running it idles fine and fires up easily.

    If I can be pointed in the right direction to start looking that would help a lot.
    Last edited by Louie1; 02-23-2021 at 06:11 AM.

  2. #2
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    1,141

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Cold start procedure
    1. Prime bulb
    2. Turn key to start crankung
    3. Push in key as you crank to engage the choke
    4. Release key once it’s running.
    you may need to raise the warm up lever slightly until the engine is running smoothly. But if everything is good you shouldn’t need much throttle.

    priming the bulb DOES NOT prime the engine. This only ensures your carb float chambers are full.

  3. #3

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Hi thanks for your response. That is pretty close to what Iím except Iím pulling the cold start lever up about 1/2 way. It fires over 2-3 times, the starter disingages but it doesnít run. I have to do this 6-7 times to get close to running. If the starter doesnít disengage and I keep turning it over while slowly increasing the cold start lever it will eventually run but even this takes a few attempts. If I squeeze the fuel bulb after several attempts at starting it is quite soft but I gather this is normal.
    Last edited by Louie1; 02-23-2021 at 10:39 PM.

  4. #4

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    A quick update, I tried cold starting it as you suggested without using the cold start lever and while winding it over it flooded. Fuel came dripping out the fronts of both carbs and the overflow tube at the base of the air box. I cleaned then tested the plugs before doing this and checked the choke was working. I’m stumped how it can be flooding with brand new needles/floats/seats in the carbs.

  5. #5
    Join Date
    Nov 2011
    Posts
    3,187

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    I suppose it could be true that different motors have different quirks, but I say that start/warm-up lever is there to be used. So, use it.

    Now as for the flooding, I am not there to see what is wrong there.

  6. #6
    Join Date
    Sep 2010
    Posts
    21,483

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Simple facts------Lots of cranking as you indicated will damage the starter.-----We are not there to observe.-----I say take the starter apart for inspection.----Load test the battery even if new.-----Inspect battery cables.-------If the flywheel does not spin rapidly there will be no spark ( intermittent / weak ) on this fine machine.

  7. #7

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Check for spark on all cylinders. These engines will run on a cylinder or 2 down. Out of the water they sound good. In the water you won’t have power. An engine with all cylinders firing will help that motor start easier.

    if you have spark on all see what rpm it is idling at. If it’s low bump it up.

  8. #8

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Thanks all. I cleaned and checked all the plugs before trying to start it and got good strong blue spark on all that would bridge a 1/2” gap except no 3 cylinder which looked weaker. Swapping plugs around indicates it’s not that plug but maybe the lead or connection problem. Would the flooding carbs be the cause of the engine not wanting to start cold?

  9. #9

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Is it likely the fuel is running out of the butterflies is just because it’s turning over without starting? I assume the needle/seat won’t stop the fuel pump sending fuel through the carb bowls if it’s not being burnt or is it supposed to dump out the bypass hose into the air box?. When I pump the bulb it remains hard for hours so would this be possible if the needles weren’t seating properly?

  10. #10
    Join Date
    Sep 2010
    Posts
    21,483

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Hold on here.-----Fuel does not DUMP out a bypass hose.-----Air going through a carburetor pulls fuel from the bowl.-----The float valves open when fuel level drops and the pump then tops up the float bowls again.-----Please read up on how carburetors / your fuel system works.-----Fuel running out of the carburetors indicates that your choke set up is working very well !!

  11. #11

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    If you’re spark is good which from what you said seems like it’s good enough. Check the choke. It’s a little black cylinder and there’s a little red valve attached to it. That choke can work one of two ways.
    with the tip of the arrow pointed down the choke solenoid is working as normal. (Push in key and it’ll choke the engine).

    if the tip of the arrow is pointed up its bypassing the choke feature (push key in) and it’s basically letting a lot of gas into the engine. It’s only supposed to be in the up position if you realize it’s broken.

    my johnson is currently running with the choke in the up position bcuz my choke valve is broken and I haven’t gotten a chance to replace it. If the tip is pointed up the engine is most likely running really rich. Check to see which way it is pointed.

    if I try to start my engine with the choke in the normal position (down) my engine is damn near impossible to start.

    if it’s pointed in the factory position (down) try starting it in the up position just for giggles and see if it turns over better

  12. #12
    Join Date
    Sep 2010
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    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    The 1978 model V-4 did not have that black primer valve ( red lever ) when it left the factory !

  13. #13
    Join Date
    Jun 2013
    Location
    Duluth Mn
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    4,237

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    So Louie, spark plugs can LOOK clean, and even spark if you test them, but still be defective. Spark plugs act differently while under compression and out of sight. Why? I haven't figured that out yet, but one sign of a bad plug is an orange or yellowish spark. I suggest you put in brand new spark plugs and give this old girl a try.

  14. #14

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Thanks for all the suggestions, I borrowed a small portable fuel tank as a test tank, hooked it up to my fuel line and bingo it starts first time and runs great. Even runs quite well tilted as far as I’d need so the problem is either the fuel connection to tank was leaking air or the pick up tube in the tank has a leak.

  15. #15
    Join Date
    Apr 2010
    Posts
    5,091

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Or you have bad fuel in your tank !!

  16. #16

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    I took the boat out for a test run today, did not go well. It ran very well in the driveway on muffs but in the water different story. It started first try then idled rough and died. I got it going by lifting the cold start lever but it was still running rough and mis firing. When I put it in gear and gave it revs it wouldn’t rev out and just bogged down. It really sounded like it was running on three cylinders. It ran like this for a few minutes and then died in gear, couldn’t get it running again without lots of key starting and cold start lever. I started with fresh fuel in the cruise tank and checked all the connections. I also had a back up fuel tank with new fuel and brand new connections, I changed over to this tank but still would not start. I’m stumped now and not sure where to look next.
    Does this sound like an ignition problem or still a fuel problem?

  17. #17

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    On the muffs back at home it still runs terribly, coughing, Mis firing and won’t idle.

  18. #18
    Join Date
    Sep 2010
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    21,483

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Flywheel key ?

  19. #19

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Thanks for the help. Is it possible for the fly wheel key to suddenly develop as a problem? I ask because the motor was running fine on two previous outings. How do I diagnose it as the cause? I have a workshop manual.

  20. #20

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    This motor only has 100 psi even all four, i know that’s low but has been since I bought the boat.

  21. #21
    Join Date
    Apr 2010
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    5,091

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    This sounds like an ignition problem. Possibly a bad power pack ?

  22. #22

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Is there a simple way to test the power packs or do I need to have a peak voltage meter?

  23. #23
    Join Date
    Apr 2010
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    5,091

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    You need a peak reading volt meter.

  24. #24

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    I ran and idled it on muffs, removed leads one by one to see what changed. Piston 1,3,4 removing the lead makes a noticeable difference to how it idled, removing lead 2 makes no noticeable difference.

  25. #25
    Join Date
    Apr 2010
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    5,091

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Find out what's missing in #2. Fuel, spark, compression ??

  26. #26

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Ok compression no worries, it has spark but how do I check it’s getting fuel?

  27. #27
    Join Date
    Apr 2010
    Posts
    5,091

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Squirt some fuel in carb throat for #2 and see what happens.

  28. #28
    Join Date
    Jun 2013
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    Duluth Mn
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    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Have you put new spark plugs in yet? Tested spark? All plugs out, looking for nice white/blue lightning like snap to 7/16". Try a #2 Phillips screwdriver in each plug boot held about 1/2" from a head bolt. Battery full charge too. If spark checks out....flywheel key is good, then your gonna find how good you are at rebuilding carbs, eh?
    Last edited by timguy; 03-03-2021 at 12:27 AM. Reason: Add info

  29. #29

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    I just checked the compressions again to rule out a sudden drop in no 2. I got 1 = 115psi, 2= 110, 3= 120, 4= 105. 2&4 are on one bank 1&3 the other if that matters so port side bank is lower psi. Sorry this may be a dumb question but When you say use a #2 philips screwdriver is that an impact driver bit ?otherwise there’s a plastic handle on a screwdriver.

  30. #30

    Default Re: 1978 85Hp Johnson is hard to start cold, easy when hot.

    Do I have to pull off the flywheel to inspect the key?

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