• If this is your first visit to the iboats.com Boating Forums, be sure to check out the FAQ. To post a question or comment, begin by signing up. To start viewing messages, select the forum that you want to visit from the selection below.


Announcement

Announcement Module
Collapse

Help Tip: If you have a question that has not been answered to your satisfaction in the archives, it is always best to start a new thread of your own. By starting your own thread, you will receive the maximum number of views by forum members.

Below are some additional forum policies in hopes of all iboats members will follow, Thank you.

1. Please do not reply to old topics or hijack existing topics. Old topics of a technical nature are like a library book, Please do not write in them.

2. Old topics should be considered archives and used for reference only. Please do not reply to them.

3. Do not take over someone elseís topic (aka hijack) with your own question, even if it is similar. If you have a question that has not been covered to your satisfaction in the archives, it is always best to start a new topic of your own.

4. If you have a question for the original poster (OP) and the topic is over 30 days old, send the OP a PM, he may not even visit the forums any longer, or may not notice your question in the old topic.

5. By starting your own topic, you will receive the maximum number of views by forum helpers that may not even notice your question when itís posted at the end of someone elseís topic. And those answers will be specific to your particular issue.

6. Please do not post to topics that have been inactive for more than 3 months unless you are the original poster. We have very active forums and any topic that remains inactive for that long should be considered "dead". It is especially confusing when there is an entirely new question posted to an old topic.

7. Posting at the end of any topic is considered to be hijacking the original posters topic which in turn subjects the topic to be closed if it continues to happen thus not making it fair to the original poster in the future had for some reason he/she needed to return for additional information or provide an update of the problem solved which is always welcomed within a reasonable amount of time frame.

8. Please note that you should see a red banner pop up near the bottom of each inactive topic asking you not to reply to old topics. The Red banner will read: Please note this topic has been inactive for 90 days. For the best results, please start a new topic.

Thank you all in advance for doing your part in helping iboats run a smooth ship.

Additional forum rules linked below.
http://forums.iboats.com/forum-rules-guidelines-405/
See more
See less

miss/sputter/hesitation at idle but runs fine at higher rpm's

Page Title Module
Move Remove Collapse
X
Conversation Detail Module
Collapse
  • Filter
  • Time
  • Show
Clear All
new posts


  • miss/sputter/hesitation at idle but runs fine at higher rpm's

    i have a 1978 Johnson 85hp motor that has a slight hickup/misfire while at idle speed, but I can throttle up and while driving it will never show itself, but once it's back down to the low rpms of idling it has a hickup where it's a momentary non fire or mis-fire. Caused it to stall once on me today. Any ideas on what it could be?
    I was thinking maybe the magneto is getting weak?

    I just put new spark plugs in it thinking that was the problem but it wasn't.


  • #2
    Re: miss/sputter/hesitation at idle but runs fine at higher rpm's

    are your spark plugs clean? 2 stroke motors are notorious for fowling plugs at idle. Also what is your idel rpm. If it is too low it may tend to sputter. Otherwise you may have to look into carburaator cleaning to make sure your idle jets are free of varnish deposits.
    Kmarine Restoration services
    1995 wellcraft martinique
    mbsports boss 210
    1998sea doo gtx

    Comment



    • #3
      Re: miss/sputter/hesitation at idle but runs fine at higher rpm's

      kmarine has provided an appropriate comment. It's common to have a "lean sneeze." An occasional miss at idle. That's a carb problem. When the engine idles, the carb butterflys are closed. The idle air is provided through the holes in the butterflys. Special dedicated idle passages cast in the upper carb body provide fuel through them-they are very small. Over years of time, they can reduce in size due to dried fuel. When these passages restrict-it will run lean and miss every few rpm's. Once you crack the throttle, even a little-other jets will provide fuel and the engine may seem to run normally. You'll need to tear the carbs down and clean out those idle passages with a carb cleaner, like the aerosol cleaner called Gumout.

      Comment



      • #4
        Re: miss/sputter/hesitation at idle but runs fine at higher rpm's

        well i just rebuilt the carbs and installed new plugs at the same time. I thought i did a good job on the carbs since I'm usually pretty good at that, but I guess I could pull them off again and re check everything. I let the bodies soak in carb cleaner for over 12 hours when i did the rebuild so I assumed they were alight.
        I've since run it about a total of 15 min since the carb rebuild and new plugs, which was yesterday. It had the "miss" before the rebuild as well, but it wouldn't idle to well and stalled when i tried to put it into gear.

        Comment



        • #5
          Re: miss/sputter/hesitation at idle but runs fine at higher rpm's

          Just curious on the quality of your fuel. Are you using fresh gas and filters ? Do you think you are running rich or lean? How many rpm is your boat idling at. Is your engine running at temperature or is it running cold or hot. There are many other things to consider when tuning, however I think you are on the right track. Make sure that your carbs are clean. I have had to rebuild carbs a couple of times and mess with float levels at times before they run perfect. Tuning is only effective if all the jets and seals are working properly. persistance is sometimes the most frustrating part of tuning 2 stroke engines.
          Kmarine Restoration services
          1995 wellcraft martinique
          mbsports boss 210
          1998sea doo gtx

          Comment



          • #6
            Re: miss/sputter/hesitation at idle but runs fine at higher rpm's

            You may want to spray the aerosol cleaner through one passage on one carb, noting the spray pattern exiting the carb. Then do that same passage on carb #2, again noting the spray pattern exiting the same orfice-comparing it with that of carb #1. Then go on to the second passage on carb #1, and repeat this process on all. You want to have the same spray pattern exiting similar passagesways on both carbs. If one is restricted, you will see it with this method.

            Comment

            Working...
            X