Results 1 to 10 of 10

Thread: Lost RPM's

  1. #1
    Member
    Join Date
    Jul 2009
    Location
    Palmer, AK
    Posts
    25

    Default Lost RPM's

    I've got a Wooly Xtra Plus with a 1990 Evinrude 150HP Outbourd Jet. Normally it would rev out at 5500 RPM. I noticed today it was maxing out at 5100. What are some reasons I might lose RPM?

  2. #2

    Default Possibly...

    Fuel starvation, carbs may need cleaned, water!! spark. There was a thread about this if you do a search you may find a few ideas.

  3. #3
    Moderator bkmail's Avatar
    Join Date
    Apr 2006
    Location
    Palmer, AK.
    Posts
    4,121

    Default

    Where you hauling a rather heavy load when you noticed the low rev on the RPM's?
    BK

  4. #4
    Member Dupont Spinner's Avatar
    Join Date
    Jun 2007
    Location
    Chugiak
    Posts
    1,425

    Default

    Check speed if still the same then the gauge is off. Check and clean grounds.

  5. #5

    Default

    Assuming you did'nt re-prop, my first suspicion is a fuel issue then, an ignition issue.

    Changed the fuel filter lately ? Checked for water in the fuel supply ?

    I would start there.

  6. #6
    Member Akgramps's Avatar
    Join Date
    Apr 2008
    Location
    Last civilized place on the planet
    Posts
    2,080

    Default Check your grates

    Grates bent on the bottom of the jet?
    I had some grates bent just enuf to let some rocks up into the jet, but were too big to pass thru the outlet.
    Funny thing was it didnt cavitate at all, just wouldnt hit max RPM......!
    Went half way to the Tolovana like that before I figured it out.......!
    They would stay in the outlet tube and can be hard to see. If you trim the motor up and get the bucket out of the way, you should be able to see if some are in there. They may fall back down to the foot if not stuck, if your lucky they will fall all they way out, otherwise you will have to minipulate them thru the grates or remove the grates.
    “Nothing worth doing is easy”
    TR

  7. #7
    Member SusitnaAk's Avatar
    Join Date
    Feb 2007
    Location
    ANCHORAGE
    Posts
    780

    Default

    I,ll say it, might be time for a compression ck, The thing is almost 20 yr,s old... Keep a eye on No#3 cyl.. I hope for the best, some days even the temp out will change a motor top rpm,s Like other,s said what was the weight rato.in the boat, that will drag them down a bit, too if you had little extra in there. Let us know what you find.

  8. #8

    Default

    I had the same problem with an older boat. Turned out to be water in the fuel. It wasnt a constant problem though. It would happen every once in a while. You might also try to use a fuel additive to clean the carbs. West marine has stuff called StarTron. Its a blue liquid and it works pretty good for cleaning and getting rid of water in fuel. BTW, does your wooly have a blue top?

  9. #9
    Member
    Join Date
    Jul 2009
    Location
    Palmer, AK
    Posts
    25

    Default isopropanol

    I had the boat out today and I actually got 5700 RPM on the Big Su. The only thing I did was add isopropanol when I topped off my fuel tank. I did have a new fuel/water seperator filter in line. Maybe it was just loaded up that day on the lake when I was only getting 5000 RPM. The boat is still new to me so I am learning as I go. I will keep an eye out and see if the RPM's stay consistant. Thanks for all your input. It is hard to troubleshoot these issues in your driveway so it is nice to hear your 2cents.

  10. #10

    Default

    Well, it certainly sounds as if water was the issue since the symptoms seems to have vanished after adding a fuel/water separator and isopropyl.

    It is something one must be vigilant against where boats are concerned.

Bookmarks

Posting Permissions

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