• 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

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

poor acceleration- cause?

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


  • poor acceleration- cause?

    1987 Johnson 88 spl. The brief recent history is overheat episode back in May, head gaskets, thermostats, water deflectors, and water pump replaced. Initally experienced misfiring due to loose powerpack ground bolt, ran much better after tightening bolt.Now the motor is very sluggish when throttle is opened suddenly. It starts fine and runs fine at low or high throttle operation, but the performance is just terrible under load (acceleration). The symptoms are confusing. When the throttle is opened up, it will "chug" irregularly as if there is an ignition miss, but after 20-30 seconds it will clear up and run with no misfiring once it reaches high rpms. Operation is very smooth at WOT after it stabilizes. Which probably means it isn't misfiring at all. Where do I start looking? I think ignition is a dead-end, although I suppose one of the components may be slowly failing. The only check I have done is ignition coil resistance and resistances are all in range and very close to each other. Also I have sprayed carb cleaner at various motor speeds and this has accomplished very little except maybe the idle operation is slightly improved.Can these symptoms be caused by a vent problem with the gas tank? The breather valve is not operating properly, and sometimes when I fill the tank with gas, the fill line overflows because the vent is not opening as pressure builds up in the tank (once the fuel fill line clears I can add more fuel, so it is obvious the tank is not venting properly). What I am thinking is the vent may be partially plugged and this may restrict fuel flow when the throttle is opened quickly.How do I fix the vent problem? The vent comes outside the boat and there is a screen and a splash guard, but it doesn't look accessible to me.Any suggestions are appreciated.


  • #2
    Re: poor acceleration- cause?

    Your symptons fit crud in the carbs. Time for a rebuild. Use the OMC shop manual.

    Comment



    • #3
      Re: poor acceleration- cause?

      As you accelerate and the motor starts to bog...try using the primer (push in on key). If the motor picks up then you've got a fuel delivery issue. As SoLittle suggests, time to remove and clean/rebuild the carbs.

      Comment

      Working...
      X