Results 1 to 10 of 10
  1. #1
    Join Date
    Aug 2020
    Posts
    5

    Default Engine Stutter - 2000 RPM - 1992 Moomba Supra

    Today after many weeks of flawless motor operation, when I was taking the boat up to the normal 3000 RPM for the spin around the lake, I noticed that at 2000 RPM the speed wasn't increasing. When I pushed the throttle further, there was a stutter or chopping noise coming from the motor. So I backed off and tried it a again, and got the same result.

    So I let the motor rest of a couple hours and went back out. This time I ran the motor at 2000 RPM for 10 to 15 minutes before increasing the throttle. Got the same feedback. Anything over 2100 RPM, the motor was chattering, almost sound like it was missing.

    Any ideas?

    Thanks,

    dbloom

  2. #2
    Join Date
    Jun 2007
    Location
    Vancouver, WA
    Posts
    5,308

    Default

    Start with popping your distributor cap and looking for corrosion. When was the last time the boat had plugs, cap, rotor, etc. done?
    You wanna live your life on the couch, or out there...

    2001 MobiusV - Ballast, Exile, Blood, Sweat & Beers

  3. #3
    Join Date
    Aug 2020
    Posts
    5

    Default

    Thanks. Doesn't have distributor cap. Was changed over to electronic ignition. Would a fuel filter be a possible culprit? or a dirty carburetor? It's just weird that when it idles, it sounds perfect. All the way up to 2000 rpm, engine is smooth. About 2300 rpm, it stutters. So I revved the engine on the lake the other day without the powertrain engaged. Same issue...

    hmmmmm...

    Thanks,

  4. #4
    Join Date
    Jun 2007
    Location
    Vancouver, WA
    Posts
    5,308

    Default

    Uh, unless you are running a new LS platform or something with coil packs it would still have distributor cap. If not, I'm super curious what you're running as I might want to upgrade!

    It wouldn't necessarily have points and condenser or an external coil any more like old school stuff, but would still have a cap and rotor at a minimum.
    You wanna live your life on the couch, or out there...

    2001 MobiusV - Ballast, Exile, Blood, Sweat & Beers

  5. #5
    Join Date
    Apr 2012
    Location
    Wake Forest, NC
    Posts
    799

    Default Engine Stutter - 2000 RPM - 1992 Moomba Supra

    My first thought is ignition as well, but if itís not it could be the secondaries in the carburetor arenít opening (if the carb has vacuum secondaries).
    2018 Murder Max
    2008 Outback V-Bought new; sold in 2018

  6. #6
    Join Date
    Aug 2020
    Posts
    5

    Default

    it doesn't have the traditional coil and cap setup .. someone replaced it with a individual coil set up for each plug.. have not pulled it apart to see if there was a bad connection / corrosion issue as of yet...

    I did pick up some Sea Foam motor treatment and a fresh 4 gallons of fuel. Dumped both of them in the tank, took her out for a spin, and no more stuttering issues. A buddy of mine was telling me that he'd had the same issue and it was the carburetor. So before I attempted to tear it down and clean it (haven't a clue how to do this), I asked my local NAPA guy what he thought. He recommended the Sea Foam.

    Will see how long this lasts. Hopefully for a while ...

  7. #7
    Join Date
    Jun 2020
    Location
    Colorado
    Posts
    17

    Default

    Could have water in the fuel.

  8. #8
    Join Date
    Jun 2007
    Location
    Vancouver, WA
    Posts
    5,308

    Default

    Quote Originally Posted by dbloom View Post
    it doesn't have the traditional coil and cap setup .. someone replaced it with a individual coil set up for each plug..
    This I still want to see.
    You wanna live your life on the couch, or out there...

    2001 MobiusV - Ballast, Exile, Blood, Sweat & Beers

  9. #9
    Join Date
    Aug 2020
    Posts
    5

    Default

    Ok I will take a pic and sent it. I pulled the coil connectors and everything is good and clean. Pulled the carburator with hope this was the issue, but after paying $350 to have it fixed (it was broken and full of gunk too), this still isn't the problem. The next thing is the plugs? God knows how long they have been in that engine. Lately I have notice a gas smell after the engine warms up for 10 minutes or when I bring it back in from cruising...

    Now I get the statement that boats are money pits, but I am enjoying learning all this stuff too ..

    Thanks,


    DB

  10. #10
    Join Date
    Aug 2020
    Posts
    5

    Default

    Good news! Life is good and the motor is running at 4600 RPM. How? Get the carburetor fixed and put in new plugs!! DuHH!!

    Yes, the carburetor was broken in a couple places. Secondary butterflies were not opening; power valve was broken; diaphragm for excelator valve was the wrong size.

    Pretty sure the gas wasn't the issue.

    She is running awesome now. Just need to figure out where the water is coming from ... do these boats normal leak a little water ??

    Thanks,

    DB

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •