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  1. #1

    MSX 140 Running max speed 33 knots (52MPH)

    With a lot of help from green hulk, I finally got my MSX engine rebuilt (well, had a motorcycle engine guy guy rebuild it for me) with a new crank and pistons, new through hull bearing seal put in, AND a jet pump alignment done.

    I broke it in nice, with a little extra oil in the tank. On the second tank of gas now. The ski had 40 hours before the engine was rebuilt, now it has about 48 hours. (~8 hours on new engine). After the first tank of gas I changed the spark plugs with brand new plugs, and yes, they are the correct NGK's. And kept the old ones as spares. They looked pretty good.

    It has a good of bottom end power, shoots right out of the water (although I dont have another MSX to compare too). Fastest I can get it to go is 45.2 knots (52 MPH). This was taken on multiple runs with a Garmin handheld GPS. I weight 200 lbs and there is no extra weight on the ski. Rarely the ski will miss at full throttle (usually it will only miss two or three times, and stop after its been riden for about 10 minutes, not counting the couple minutes I let it warm up at idle).

    I adjusted the throttle cable so throttle plates are full open when trigger is squeezed all the way. I adjusted the TPS sensor by turning it counter clockwise all the way and tightening the bolts.

    RPMS are about 6750-6800 constant at full speed, sometimes hitting up to 6850-6900 for a few seconds at a time.

    Compression is 100 psi on rear cylinder, 110 psi on middle cylinder, and 105 psi on front cylinder. Seems kind of low to me, or is that right? Spark plugs (these plugs have only been in for about 3 hours) are black on one side, white on the other, except the rear spark plug which is black on one side, ORANGE on the other. Coincidentally, the reason we rebuilt the motor was that the rear cylinder blew, Polaris slapped a new cylinder piston and rings on it, and it blew again 1 hour into the break in, so I rebuilt again using a new crank. Full set of new gaskets was used on my rebuild.

    The impeller does not look damaged at all. Maybe a few tiny scratches on the leading edge, but nothing drastic.

    Can I use a plain old fuel pressure checker for a fuel injected auto on that schrader valve? Any special adapters? Just want to be sure before I go spend $75 on another one time use tool...

    What could be wrong? Where do I start looking? Is the 100-110 compression too low? I am getting good rpm's. What does that mean, and why is my speed not as high as it used to be?

    Also, one more question: Is there oil in the crankcase, and how do I replace it? Anything else to do after the accidental flooding in fresh water (one of the exhaust hoses was not clamped down and it finally came loose yesterday... flooded it, but the speed issues were happening before that)


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Accidental flooding - water in the hull only, or water into the actual engine?

    Your RPM seem right where they should be at WOT. Is the impeller the stock part number? Have you checked impeller blade clearance to the surround wear ring?

    Was the jet pump BASE section removed from the hull?

    What intake grate is installed?

    Compression numbers suggest the gauge may be inaccurate.

    Does the GPS report accurate speed numbers when tested in a car?
    Are you monitoring the GPS speed display while you ride, or depending on the GPS 'max speed' recording feature?

    The missing at full throttle suggests something is not quite right. Has the TPS been changed?
    Has the EMM ever been repaired or replaced?

    Spark plug tips can be hard to read, especially on the Ficht engines. What do the piston wash patterns look like?

  3. #3
    Accidental flooding - water in the hull only, or water into the actual engine? - Water in the hull. Lots of it. up to the bottom of the cylinders. I hope nothing seeped into the engine. But, after I drained it it has been running fine, just like before, SO i dont THINK it caused any problems, but just wanted to be sure there is nothing I can do other than a spray down.

    Your RPM seem right where they should be at WOT. Is the impeller the stock part number? Have you checked impeller blade clearance to the surround wear ring? Impeller is stock, and I have not checked the clearance. I would love to check this, I will have to look up some info on how to do this, unless someone has the link to the post already

    Was the jet pump BASE section removed from the hull? - YES it was. I used 5200 slow dry silicone on it when I put it back. Is there something here I missed?

    What intake grate is installed? - The stock one

    Compression numbers suggest the gauge may be inaccurate. - Very possible, it is a snap on guage, but it has been sitting outside for a while.

    Does the GPS report accurate speed numbers when tested in a car? - yes, the gps is accurate, tested against the gps in the boat and another handheld. Right on the mark with the others.

    Are you monitoring the GPS speed display while you ride, or depending on the GPS 'max speed' recording feature? Monitoring while I ride, hunched down, GPS in the left hand.

    The missing at full throttle suggests something is not quite right. Has the TPS been changed? Yes new tps was installed.

    Has the EMM ever been repaired or replaced? Emm has never been replaced or repaired

    Spark plug tips can be hard to read, especially on the Ficht engines. What do the piston wash patterns look like? I will pop off the heads tonight and take some pictures.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Fuel pressure can be checked with any fuel pressure gauge that will fit the schrader valve. Expect a little over 20 PSI, stable pressure with engine running.

    Since you have the typical engine RPM at full throttle (which implies the engine is producing the expected HP) my thinking is that either the jet pump isn't producing the expected thrust or something is creating more hull drag than normal.

  5. #5
    how close should the impeller blade be to the wear ring? what is too much?

    K447 asked Was the jet pump BASE section removed from the hull? and i did in fact remove it. what kind of problems could this have caused?
    Last edited by K447; 06-14-2011 at 12:46 AM.

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by aksobe View Post
    how close should the impeller blade be to the wear ring? what is too much?

    K447 asked Was the jet pump BASE section removed from the hull? and i did in fact remove it. what kind of problems could this have caused?
    Maximum impeller blade clearance is .020 inches,optimal is .010 inches or less.

    If pump base and ride plate are not well sealed to hull then air leaks can cause jet pump ventilation, which reduces thrust, mostly when accelerating from low speeds.

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