Starting Problems: Yamaha 90 HP 2-Stroke

Discussion in 'Outboard Maintenance' started by DBStoots, Jan 2, 2012.

  1. DBStoots

    DBStoots I Love microskiff.com!

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    I have a 90HP Yamaha 2-Stroke on the back of my HPX-V 17. At the ramp, it's almost always hard to start, but on Saturday it was particularly troublesome. The motor turns but doesn't seem to fire for quite a while. The plugs are new. I've only used non-E fuel. Only used Yama Lube Oil. One the boat starts and warms up, every successive start is first crank. I'm thinking maybe the engine utilizes an oil level sensor switch that impacts the ignition control module, so because the engine has been tilted up in transport to the ramp, maybe the sensor is telling the engine there is insufficient oil and this affects the exact spark timing. Could that be the problem? Any other suggestions? The engine runs like a champ otherwise once it is started and warmed up.
     
  2. Brett

    Brett > PRO STAFF <


    If it's not choke/primer related, then it sounds like there's not enough fuel in the system when cold.
    As stated it takes a lot of cranking to start it. Sounds like the amount of time it takes to get the fuel system primed
    to the point where it makes it to the pistons. When warm, fuel system is still full from last use.
    If it's not holding prime overnight, then I'd be looking for a small airleak or a failing backflow valve.
     

  3. DBStoots

    DBStoots I Love microskiff.com!

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    Thanks, Brett. I'll check it out.
     
  4. Creek Runner

    Creek Runner Well-Known Member

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    I would be looking at the primer system, the 90 2s uses a primer thermo system wired to the key switch, when the key is turned on the primer allows fuel to flow when the engine is cold, if you look on the front on the engine with the cowling removed you will see a red switch with 3 positions on, off, and manual. Try switching to on during the 1st start, and see if this helps. If so make sure you have power going to the Thrermo switch when switched on.

    Also always make sure your primer bulb is hard before prior to starting.
     
  5. DBStoots

    DBStoots I Love microskiff.com!

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    No problems on Sunday at the ramp in Flamingo. I squeezed the primer bulb a little more than usual, and probably more important, used the choke. I think in the past I really wasn't taking advantage of the choke. Thanks for all of the input.
     
  6. Creek Runner

    Creek Runner Well-Known Member

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    Dave I'm glad the engine started easy for you on Sunday. The best thing you did was pump the primer bulb sufficiently. However your engine does not have a choke, at least 1 that you can utilize; Read my above post on how your choke systems works
     
  7. DBStoots

    DBStoots I Love microskiff.com!

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    Thanks. Isn't there a choke integrated with the main key switch? I thought the choke circuit operates when the main starter switch is depressed as it rotates to start. The engine is a 2007 Yamaha 90 HP 2 stroke.
     
  8. levip

    levip I Love microskiff.com!

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    it does sorta

    make sure youve got a FULL charge on your battery the night before you head out. the ignitions on these jap motors are VERY sensitive to low voltage and wont throw a good spark in cold weather ESPECIALLY if the battery is down a bit

    itll seem like its turning fast enough but it isnt - i had this problem with my tohatsu a time or two and the remedy was to charge my battery the night before
     
  9. Creek Runner

    Creek Runner Well-Known Member

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    Depressing the Key switch does nothing on your engine, it's controlled by a Thermo Switch (The prime start device works like this, there is a small fuel pump on the center carb, (where the manual enrichment is, small red valve see my previous post on how to use this) When the engine is cold, and the key is switched to the ON position, the needle valve on the electro thermal valve the thing with the blue and black wires in it mounted on the middle carb is retracted, this opens up a passageway and allows fuel from the small pump to be sent down a hose to the intake manifold, as the motor runs, voltage from the battery charging coils in the stator, warms a wax pellet in the electro thermal device and this pushes the needle valve slowly to seat cutting off the extra fuel. Pushing in your key switch does nothing but push in the key switch.


    The 90 Yamaha 2stroke CDI is not sensitive to low voltage, as long as your turning fast enough to crank your ok.
     
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