• 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.
  • ALL iboats Forum Members and Guests:
    To show our appreciation for your participation in the Forums, we're offering an exclusive Forums-only discount good for an additional 5% off your iboats.com order for a limited time.
    To redeem, simply call our Customer Service Team at 800-914-1123 (Open M-F, 9am - 8pm Eastern Time) and mention the Forums 5% off discount. Offer excludes engines, trolling motors, and electronics.


Announcement Module

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 threads or hijack existing threads. Old threads of a technical nature are like a library book, Please do not write in them.

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

3. Do not take over someone elseís thread (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 thread of your own.

4. If you have a question for the original poster (OP) and the thread 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 thread.

5. By starting your own thread, 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 thread. And those answers will be specific to your particular issue.

6. Please do not post to threads that have been inactive for more than 3 months unless you are the original poster. We have very active forums and any thread 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 thread.

7. Posting at the end of any thread is considered to be hijacking the original posters thread which in turn subjects the thread 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 thread asking you not to reply to old threads. The Red banner will read: Please note this thread has been inactive for 90 days. For the best results, please start a new thread.

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

Additional forum rules linked below.
See more
See less

150 Black Max idle too high...how to adjust?

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

  • 150 Black Max idle too high...how to adjust?

    As the title says I have a 1983 150hp Mercury Black max that runs awesome and idles good....just higher than the recommended rpm's. So my question is how do I adjust the idle to be lower? idle adjustment screw/s? it says no more than 750rpm while in gear and im quite a bit higher than that. any info would be great!

  • #2
    Re: 150 Black Max idle too high...how to adjust?

    The idle is set by adjusting the intial timing. 750 RPM in gear means in the water and under normal load. On the hose out of the water an idle of 850 is recommended. The intial timing adjustment is done using the single screw located just below and to the right of the large pivot bolt on the throttle arm. This is the only place you should ever attempt to adjust the idle. However, and there's always that however thing, being able to adjust the idle successfully depend on correct link and sync adjustment. If that's been messed with or wasn't done correctly you'll never get the idle where it needs to and have it remain smooth.

    90% of the time when an older engine doesn't idle at the right RPM its because someone has done the link and sync procedure incorrectly and one of the carbs isn't closing completely. I see this quite often.


    • #3
      Re: 150 Black Max idle too high...how to adjust?

      The idle pick up screw (just below the pivot) is set during link n sync. Normally it doesn't need to be messed with.

      Several things will affect your final idle.

      One is water, which puts a small amount of back pressure on the exhaust, so you need to adjust it in the lake.

      Another is throttle cable adjustment. Take the cable off for idle adjustment, then adjust the cable and put it back on.

      The idle adjustment screw is the one on the very bottom of the throttle arm assembly.

      If it doesn't seem to set up right, you should get the book and go through the formal linkage and timing adjustments. Then it'll probably work just like new.

      hope it helps