ob motor bogs down

Discussion in 'Outboards' started by cat nap2, May 31, 2019.

  1. cat nap2
    Joined: Nov 2015
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    Location: Orange,Ct

    cat nap2 Junior Member

    I have a Handa bf25a outboard motor on a sailboat. It's 20years old but ideals and runs fine.
    It's 3cyl 3carb motor. We have ethanol gas in the US so I use gas extender and carb cleaner all the time. All of the carbs have been changed at some point.
    The problem is that when the motor is shifted into gear the motor Boggs down (will not rev up). If I
    play with the the throttle sometimes it will rev up but sometimes it stalls. It always starte up in neutral.
    Any suggestions ???
    Thanks. Nick
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    The idle setting may be too low, but you should obtain a manual for the engine before making any adjustments.
     
  3. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    Old motors weren't designed to run on gas with ethanol in it. Hoses and fuel pump diaphragm rubber is not compatible with ethanol. The rubber inside the hoses flakes off and can clog the jets. Diaphragms can crack and the pump will fail. Many of these old motors have rubber tipped needles on the carb floats. Ethanol in the gas will destroy the rubber and the float setting will now be correct, and this can cause flooding.

    Adding a fuel stabilizer and carb cleaner does not help if the hoses and fuel pump is not compatible with ethanol laced fuel. The hoses and rubber parts will still deteriorate because the stabilizer doesn't get rid of or change the ethanol they just make it less likely to absorb water.

    The first thing to do is to take off some of the fuel hoses between the pump and the carbs and see if there is any deterioration or flaking rubber inside the hoses. Then you are going to need to tear down the carbs and clean them. Then you need to replace all the hoses, the fuel pump diaphragm and determine if the needles and seat for the floats are rubber tipped.

    If you have an old motor you need to be religious and run it on ethanol free fuel If you have to run it on ethanol fuel, after a few seasons you're going to have problems with fuel line deterioration and other problems. The fix is to buy new parts that are ethanol compatible. If those aren't available you're going to have to use NOS hardware that isn't compatible and then make sure that you use ethanol free fuel in it in the future. You can find ethanol free fuel if you go to www.pure-gas.org and find ethanol free gas near you.
     
  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Compression test.

    If it passes; change plug, carb kit.
     
  5. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    I'm tipping if the problem doesn't occur when the engine is started out of the water, the idle setting is too low. They lose several hundred revs by immersion.
     
  6. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    Some of the 4 strokes have accelerator pumps, if it fails it can cause bogging or dying during acceleration.
     
    Last edited: Jun 2, 2019
    fallguy likes this.
  7. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    It's a 2 stroke, has to be. It's a 3 cyl with three carbs... Nobody does that with a 4 stroke...

    Fall guy is right, the first order of business is to look at the plugs. If it has any wet plugs you can change them out first, as the problem could just be a bad plug and that would fix it. Plugs in a 2 stroke don't last forever, the oil fouls them. People have been spoiled by unleaded fuel, cars that go 100,000 miles on a set of plugs now. Back when we had leaded fuel plugs lasted 3,000 miles. That has to be the first step.

    While the plugs are out you can do a compression test if you have a compression tester. Note that small two strokes need a compression tester with a one way valve near the plug hole or a very short hose. Some testers have long hoses and the one way valve near the gage. These are worthless on a smaller engine.

    If all the plugs are dry then he needs to be careful. A multi carb 2 stroke with a clogged carb isn't getting fuel to the cylinder that had the bad carb and it isn't getting any lubrication either. If it's a clogged carb hopefully he hasn't run it much and hasn't damaged the rings, the compression test will tell the story there. I'm also assuming that the engine starts and appears to idle ok. If it's not running smooth or if it is loping at idle, or if the idle speed is low then it is also likely that a carb is clogged up.

    If he is jinking with the throttle and the motor takes off it is more likely that the low speed jet has clogged and once it gets on the high speed jets he's got fuel.

    Outboard racers use a small oil squirt can and put 2 stroke mix in it. Then you can start the engine and squirt some fuel into each carb and see if the engine speeds up when you squirt some fuel with lube in it into the intake. That will isolate the bad carb, but if the fuel lines are deteriorating then the other carbs will start clogging up in short order.
     
  8. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    Honda doesn’t make 2 strokes.

    And outboards have been E-10 compatible since around 1990, although any parts that old should be replaced anyhow.
     

  9. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Certainly right about Honda being 4S only. Still sounds like the idle is too low to me, the cable can get a bit of slack in them with wear, and the idle drops too low.
     
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