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  1. #1

    SHO dies at slowly throttle

    Have trouble with a SHO Cruiser, it dies if I give him a slowly throttle. If I pull the throttle quick it keeps alive. What I tried till now, I changed the injectors, the ECU, sparks, checked the manifold ribbon and the gastank for dirt, made a compression test, changed the throttle accelerator body, all parts from a boat which works, checked with diagnostic system the faults and also the amounts of the accelerator bodies, everything is fine. The warmer the engine becomes the better it is, but not acceptable. The boat was used in saltwater but I cannot see big corrosion. Any idea ???


  2. #2
    64physhy's Avatar
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    Do you have any modifications to it? How many hours are on it?

  3. #3
    Kelly_A's Avatar
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    Might be a malfunctioning throttle position sensor (there are 2) or accelerator position sensor (2 also, but combined in a single unit).
    These parts can be checked using a VOM, but the information you'll get is limited. Your best bet is to take the ski to a dealership and have them hook it up to their YDIS. The dealer will check these with the engine off, which may be why you're not seeing a code with the onboard diagnostic system.

    Last thing I can think of is a bad (or loose connection) to the electronic throttle valve relay, which is inside the electrical box that contains the ECM. If you've removed your electrical box at any point, that connection might be worth checking. It's located to the left of the top of the ECM (when facing the rear of the ski). Service manual outlines how to use a VOM to verify input voltage and relay continuity.

  4. #4
    The boat has 32 hours, I built in a E1 Supercharger wheel and flashed the ECU, but with an ECU from a stock boat it is the same problem. I am Yamaha dealer and have the YDIS to test it, it doesn´t show me any errors and the voltage of the TPS and APS is normal, I also compared it to a working boat.

  5. #5
    Kelly_A's Avatar
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    Using a VOM, if the ETV relay checks good for continuity and ETV relay connector input voltage is good, I'm out of ideas.

  6. #6
    64physhy's Avatar
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    Shouldn't you be running a powershot and fuel regulator with the E1 wheel?

  7. #7
    no, I have a flashed ECU, on other boats this setup works perfect

  8. #8
    Kelly_A's Avatar
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    This problem began immediately after installing the E1?
    I'm assuming some sort of aftermarket air intake has replaced the stock air box?
    Will the problem happen when the ski is on the trailer and not under load? (I know, kinda hard to tell since you really don't want to rev it that high..)

  9. #9
    it happens on the trailer, I do not know if it was before, the customer brought it to tune it, I also started it before, but I did not give em a throttle on the trailer before I worked on it. The client told me that the boat worked fine before he put it in the garage last season, he did not winterize it and brought it now to me to tune it, before he wil use it first time

  10. #10
    Kelly_A's Avatar
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    OK, so assuming the actual owner is telling the truth, the ski ran fine before it was put up for winter (but not winterized). It's been used in saltwater, so more than likely it's a corrosion problem with one of the sensors, coupler connections or the harness.

    The problem lessens when the engine is hot so it's something that's close enough to the engine to be effected by heat (which pretty much rules out anything in the electrical box and most of the harness). That tends to point to an electrical fault with the ground or coupler connection on one of the sensors - as metal expands w/ heat, connection improves slightly.

    Since the problem doesn't appear when you nail the throttle, it follows that it has to be one of the sensors that goes to 0 resistance, or opens the circuit, under full throttle - but sends an incorrect reading under partial throttle.

    You may just have to pull sensors one at a time and check for corrosion on the sensor itself and on the connector. Also, although unlikely, it can't hurt to double check the condition of the main ground at the starter.

    I have no idea why your YDIS isn't showing anything. I've never used one, but thought they were omniscient.

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