Results 1 to 4 of 4
  1. #1

    Join Date
    Jan 2010
    South Carolina, USA

    MSX 150 wont turn over 4300 rpm?

    got a pair of msx 150s, don't know any history behind them, but neither will turn over 4300 rpms and the warning light is blinking. I have scrolled thru the msx posts and have only found one close to my problem and he claims to have spent over 4 grand to fix. can anyone give me some advice?

  2. #2
    Moderator HiPeRcO's Avatar
    Join Date
    Jul 2007
    Upstate NY
    Does the engine light stop blinking after 10 seconds when you first start it up? Then does it go on once you give it throttle? If so, you could be hitting overboost due to a bad boost valve (common issue).

  3. #3
    ripcuda's Avatar
    Join Date
    May 2010
    Newman Lake, WA
    Well... at least you have 2 so you can swap parts to figure stuff out!

    I'm assuming your max RPM is what you see in the water, right? (not on the trailer?)

    First things first... with all Weber MSX. Do a compression test. Both plugs out, squeeze throttle to full while cranking. Report your #s. You want to see 125+ psi and even.

    Check your oil level.
    - any foam or heavy-milky oil on the dipstick?
    - If overfilled (very common) it will cause foaming which leads to the dreaded oil ingestion and tons of headaches where the engine won't run right. Oil level is best check with a hot engine where you want it between MIN<>MAX but not all the way at MAX. On a cold engine, start for 30 secs and turn off... pull dipstick, insert (do NOT screw in), pull and read. You want the oil just barely on the dipstick... definitely below MIN.

    Premium fuel only. Mobil 15w-50 synthetic oil only (or RotellaT 15w-40 for flushing).

    What plugs do you have in it?

    Any oil slick floating on the top of the coolant in the coolant jug? Coolant jug level staying constant...ever having to add coolant?

    Pull intercooler to intake hardpipe off. Inspect inside the pipe for oil gunk. Check the hardpipe MAP and ensure it's clean. Heavy oil layer or gunk is sign of oil ingestion.

    Pull the jet pumps. 4 LONG bolts (unhook reverse, steering and bilge siphon hoses first). Ensure good impeller to wear ring clearance. Thin cereal box cardboard is ~.018"... that's max gap it should be... less is better. Ensure the impeller spins smoothly.

    Check all this stuff and let us know what you find.


  4. #4

    Join Date
    Jan 2010
    South Carolina, USA
    ok, thanks guys for the info and starting point, ive never worked on a weber engine, so thanks for sharing and the help. I will check the formentioned items and return back.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. polaris MSX 150 wont rev over 5800
    By msx150lover in forum Polaris Open Discussion
    Replies: 34
    Last Post: 08-03-2017, 02:19 AM
  2. 2006 seedster 150 155HP wont go over 6600 RPM
    By terryor in forum Sea Doo Sport Boats
    Replies: 2
    Last Post: 06-23-2015, 11:51 PM
  3. Ultra 150 wont turn over
    By windwalker117 in forum Kawasaki PWC Performance (2-stroke)
    Replies: 6
    Last Post: 08-14-2012, 09:48 PM
  4. 2004 MSX 110 wont run over 3500 RPM?
    By krw1045 in forum Polaris How To & FAQs
    Replies: 4
    Last Post: 05-30-2012, 04:59 AM
  5. Polaris MSX 110 Wont go above 4300 RPM
    By Drummerdarwin in forum MSX/Matrix
    Replies: 27
    Last Post: 08-30-2009, 06:30 PM

Posting Permissions

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