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  1. #1

    Default 1977 55 hp Johnson surging at WOT

    Hello~
    A quick history on the motor; bought a few years back from a guy, it did run but the prop wouldn't turn in either forward or reverse. The engine sat for a while, then I finally had some time this spring to disassemble the lower unit and see what was what. Well, turns out the pinion gear and the forward gear were mush. So, with all new parts I was able to completely rebuild the lower unit and get that back on. I have also installed a new fuel pump and rebuilt both carbs, and new spark plugs too. Any history beyond that, I have no idea. The motor runs very good at low and mid range RPM's, however when I go WOT after a few seconds, it surges for a few seconds then drops RPM's on it's own. If I back the throttle off, to a mid range or low range, the problem goes away until I go WOT again. I have searched the forums here and my best guess is that has something to do with timing? Any thoughts or advise would be greatly appreciated! I do have a video of it, but I couldn't figure how to upload to this site. I could email if that would help.
    Thanks,
    Chris.

  2. #2

    Default Re: 1977 55 hp Johnson surging at WOT

    Did you physically clean out the high speed jets in the carbs?

  3. #3

    Default Re: 1977 55 hp Johnson surging at WOT

    That's the one thing I could not do. If I remember right, I couldn't get them to come out.

  4. #4
    Join Date
    Sep 2010
    Posts
    19,787

    Default Re: 1977 55 hp Johnson surging at WOT

    Well----The timing on these motors is fixed at the factory.-----Owners generally should not attempt making adjustments.----Trying to change timing with the ---" Lets see what happens " if I turn this , just does not work.----Test run with another tank and hose.------

  5. #5

    Default Re: 1977 55 hp Johnson surging at WOT

    Good to know. I'll forget about messing with that then. Gas tank, hose and gas is brand new. Maybe I'll buy another tank and hose and try that. Perhaps re-do the carbs again and see if I can get the high speed jets out this time.

  6. #6
    Join Date
    Sep 2010
    Posts
    19,787

    Default Re: 1977 55 hp Johnson surging at WOT

    Test run with a timing light hooked to one cylinder at a time.----Observe the flashing light and look for possible spark issues.

  7. #7

    Default Re: 1977 55 hp Johnson surging at WOT

    Yeah, a timing light is one tool I don't have anymore. I'll have to grab one!

  8. #8

    Default Re: 1977 55 hp Johnson surging at WOT

    Quote Originally Posted by mudhunter View Post
    Yeah, a timing light is one tool I don't have anymore. I'll have to grab one!
    Disregard this post. For some reason pictures are not being uploaded.
    Last edited by mudhunter; 07-15-2020 at 04:56 PM.

  9. #9

    Default Re: 1977 55 hp Johnson surging at WOT

    The high speed jets, those are the lower one's correct? Below the butterfly? And they're removed with a standard screw driver?

  10. #10
    Join Date
    Sep 2010
    Posts
    19,787

    Default Re: 1977 55 hp Johnson surging at WOT

    The high speed jets ( orifice plugs ) are inside the carburetor bowl.-------Found way inside after taking the drain screw out.------A 3/16" diameter screwdriver may work or modify one to take them out.

  11. #11

    Default Re: 1977 55 hp Johnson surging at WOT

    Quote Originally Posted by racerone View Post
    The high speed jets ( orifice plugs ) are inside the carburetor bowl.-------Found way inside after taking the drain screw out.------A 3/16" diameter screwdriver may work or modify one to take them out.
    Yeah, those are the one's I think I couldn't get out. I'll take the carbs off again after work and try again. And these don't generally come in rebuild kits if I remember right?

  12. #12

    Default Re: 1977 55 hp Johnson surging at WOT

    Quote Originally Posted by racerone View Post
    The high speed jets ( orifice plugs ) are inside the carburetor bowl.-------Found way inside after taking the drain screw out.------A 3/16" diameter screwdriver may work or modify one to take them out.
    Thanks for the advice! They were both pretty gummed up. We'll see how she does today!

  13. #13

    Default Re: 1977 55 hp Johnson surging at WOT

    Well, after installing all new jets and new carb kits she purrs like a kitten. Took her out this morning on the river and im happy to say, problem solved! I can't thank you all enough for your wealth of information and wisdom.

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