Yamaha 25hp 4 Stroke help

Discussion in 'Outboard Maintenance' started by wadeleebenton, Aug 9, 2011.

  1. wadeleebenton

    wadeleebenton I Love microskiff.com!

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    When I start my motor it will only run just a bit over idol speed for 10-15 minutes until it eventually will get up to full speed. This has happened the past 3 times Ive had the boat out. I thought it might have been bad gas so I got new gas, didnt help. After the initial time getting the motor "warmed up" it works better but still takes time to get up to full speed. It will be running slow then kind of starts surgeing a little bit then starts running fast.

    Any ideas?
     
  2. Brett

    Brett > PRO STAFF <

    I think your fuel system isn't functioning properly.
    My guess, without any further information, is that something
    is restricting the flow of fuel to the carb(s).
     

  3. wadeleebenton

    wadeleebenton I Love microskiff.com!

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    Any ideas on where I should start checking first?
     
  4. Brett

    Brett > PRO STAFF <

    Fuel lines from tank to carb(s).
    Airleaks, blocked filters, bad fuel pump, sealed fuel tank (vent not open)

    My troubleshooting checklist from a previous post:
     
  5. DuckNut

    DuckNut Brandon, FL

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    I would not be looking for an obstruction because you mention that it eventually gains rpm's and it takes less time when warm. My guess is that the little gasket around the needle vlave in the float is rotting and turned to a gummy substance and is sticking.

    Take the bowl off and remove the float and the needle valve and remove the o-ring and reassemble and start. If you get rpm's right away that was your problem. Your motor will not idle down or run right with this piece out, but it may give you a starting point. Some carbs have a rubber tip on the valve - if this is yours then clean it well and spray some cleaner where it seats and reassemble and test. Either way it is a 10 minute experiment.

    The o-rings are made from two types of material; neoprene and rubber. Neoprene rings are not long lived with gas.
     
  6. wadeleebenton

    wadeleebenton I Love microskiff.com!

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    Thanks guys! This will give me a start on a weekend project.
     
  7. wadeleebenton

    wadeleebenton I Love microskiff.com!

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    So how do I pressure test the fuel pump? I'm pretty sure thats my problem but want to make sure before I get a new one.
     
  8. Brett

    Brett > PRO STAFF <

    http://www.microskiff.com/cgi-bin/yabb2/YaBB.pl?num=1300667925/5
     
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