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  1. #1
    Join Date
    Apr 2003
    Location
    The Gareloch
    Posts
    3,802

    Default ‘Tight’ Outboard

    I have a Yamaha 2hp 2-stroke which, up until recently, has behaved impeccably. This week, however, it has been hard to start. For the first few pulls it feels tight, very hard to get a decent long hard pull for it to start.
    After a few pulls it frees up and eventually starts and runs, but not as well as it used to.
    It won’t run between the turtle and the start throttle positions; it just dies.
    Push the throttle up towards the hare and it runs for a while, 5 minutes or so, before fading and stopping. I can start it immediately, but it still feels tight.

    I’m running it on the recommended 100:1 mix and the engine’s never been dunked.

    Where do I start looking?

  2. #2
    Join Date
    Apr 2018
    Location
    Mooring, Faro
    Posts
    1,487

    Default Re: ‘Tight’ Outboard

    I would start by running it on 50:1 and see if it frees off, could even try 25:1. Has it overheated? Is the thermostat blocked or faulty?

  3. #3
    Join Date
    Sep 2001
    Location
    Me - Zumerzet Boat - Wareham
    Posts
    12,159

    Default Re: ‘Tight’ Outboard

    Sounds like fuel starvation to me.
    So possibly
    Blocked jets
    If it has a filter between tank and carb, check / bypass that.
    Is this after a new mix of fuel, if so check it for contamination and 'glueing', make up a new mix.
    I don't agree with changing the mix ratio for this problem, I've always used 100/1 without issue, I have always had tightness on first 4 or so GENTLE pulls, I never pull hard and the engine starts on 5th or 6th gentle pull.
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  4. #4
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,443

    Default Re: ‘Tight’ Outboard

    Quote Originally Posted by Porthandbuoy View Post
    I have a Yamaha 2hp 2-stroke which, up until recently, has behaved impeccably. This week, however, it has been hard to start. For the first few pulls it feels tight, very hard to get a decent long hard pull for it to start.
    After a few pulls it frees up and eventually starts and runs, but not as well as it used to.
    It won’t run between the turtle and the start throttle positions; it just dies.
    Push the throttle up towards the hare and it runs for a while, 5 minutes or so, before fading and stopping. I can start it immediately, but it still feels tight.

    I’m running it on the recommended 100:1 mix and the engine’s never been dunked.

    Where do I start looking?
    Do a compression test. You may find that 100:1 has taken its toll over the years especially if not fogged before storage.

    Quote Originally Posted by Graham376 View Post
    I would start by running it on 50:1 and see if it frees off, could even try 25:1. Has it overheated? Is the thermostat blocked or faulty?
    I dont think there is a thermostat

  5. #5
    Join Date
    Apr 2003
    Location
    The Gareloch
    Posts
    3,802

    Default Re: ‘Tight’ Outboard

    There isn’t a thermostat and there’s plenty water coming out of the tell-tale.

    At the end of each season it’s run in fresh water and some 3-in-1 squirted down the plug hole.

  6. #6
    Join Date
    May 2001
    Posts
    14,356

    Default Re: ‘Tight’ Outboard

    I learned the hard way that with 2-stroke engines to never stop the motor unless you first turn off the fuel. When I didn't do that, the fuel in the carb evaporates leaving a tiny bit of oil behind and this coagulates. Over time, this accumulates to the extent that when I took it apart I saw what looked like an O-ring around the jet. I cleaned it off and the 'needle' was, once again, free to move.
    I'm not saying that this is what happened in your case but it's worth a try.

    P.S. I too have an ancient Yamaha 2. My problem is that the outside of the cylinder has corroded, making the water leak from the water jacket. I intend to clean the opening back to 'virgin' metal and plug the hole with chemical metal, thickened epoxy putty or something similar. I don't know if this will work. Perhaps someone can suggest a better solution. Thanks.
    Last edited by PuffTheMagicDragon; 17-07-19 at 14:42.
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  7. #7
    Join Date
    Sep 2011
    Location
    west midlands
    Posts
    1,024

    Default Re: ‘Tight’ Outboard

    Quote Originally Posted by PuffTheMagicDragon View Post
    I learned the hard way that with 2-stroke engines to never stop the motor unless you first turn off the fuel. When I didn't do that, the fuel in the carb evaporates leaving a tiny bit of oil behind and this coagulates. Over time, this accumulates to the extent that when I took it apart I saw what looked like an O-ring around the jet. I cleaned it off and the 'needle' was, once again, free to move.
    I'm not saying that this is what happened in your case but it's worth a try.

    P.S. I too have an ancient Yamaha 2. My problem is that the outside of the cylinder has corroded, making the water leak from the water jacket. I intend to clean the opening back to 'virgin' metal and plug the hole with chemical metal, thickened epoxy putty or something similar. I don't know if this will work. Perhaps someone can suggest a better solution. Thanks.
    I'm guessing there is a restriction in the drive train, either in the gearbox or more likely in the driveshaft tube. If you can remove the gearbox (old 2hp can be a pain with driveshaft tube seizing on the water pump). Pull the engine over. If it's still not free you have an issue with the powerhead

  8. #8
    Join Date
    May 2001
    Location
    North from the Nab about 10 miles
    Posts
    8,835

    Default Re: ‘Tight’ Outboard

    Quote Originally Posted by steve66 View Post
    I'm guessing there is a restriction in the drive train, either in the gearbox or more likely in the driveshaft tube. If you can remove the gearbox (old 2hp can be a pain with driveshaft tube seizing on the water pump). Pull the engine over. If it's still not free you have an issue with the powerhead
    I agree with Steve, OP says its harder to pull over. That wouldnt be a mixture issue. More likely something like fishing line caught on the prop hub, or an internal fault in the drive train as Steve suggests. A worse case scenario is one of the engine bearings binding. That can easily be eliminated once the drive leg has been separated from the power head. If it turns over normally (take the plug out, and it should spin freely), then its something binding in the leg.
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  9. #9
    Join Date
    Apr 2003
    Location
    The Gareloch
    Posts
    3,802

    Default Re: ‘Tight’ Outboard

    Quote Originally Posted by steve66 View Post
    I'm guessing there is a restriction in the drive train, either in the gearbox or more likely in the driveshaft tube. If you can remove the gearbox (old 2hp can be a pain with driveshaft tube seizing on the water pump). Pull the engine over. If it's still not free you have an issue with the powerhead
    Quote Originally Posted by oldharry View Post
    I agree with Steve, OP says its harder to pull over. That wouldnt be a mixture issue. More likely something like fishing line caught on the prop hub, or an internal fault in the drive train as Steve suggests. A worse case scenario is one of the engine bearings binding. That can easily be eliminated once the drive leg has been separated from the power head. If it turns over normally (take the plug out, and it should spin freely), then its something binding in the leg.
    I’ve checked the prop hub; nothing tangled there and the carb’s as clean as a whistle.
    Even with the plug out the engine feels stiff.
    Looks like I’ll have to split the drive leg and power head to narrow it down.

  10. #10
    Join Date
    Apr 2004
    Location
    Portchester, Solent
    Posts
    5,009

    Default Re: ‘Tight’ Outboard

    Quote Originally Posted by Porthandbuoy View Post
    I’ve checked the prop hub; nothing tangled there and the carb’s as clean as a whistle.
    Even with the plug out the engine feels stiff.
    Looks like I’ll have to split the drive leg and power head to narrow it down.
    I had a similar problem, it turned out to be in the impeller housing. The surrounding alloy had corroded and squeezed the stainless lining causing the impeller to bind inside the pump.

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