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  1. #1

    Question BF25 loses power when under a load

    My BF25 has been in and out of the Honda Repair Shop four times in the last two months. They are now guessing as to why it losses power while running perfect for say 30 mins @ 100% throttle, then out of the blue it loses power and hunts as if its starving for fuel. The problem gets even worse if it experiences more load demand (while motoring up and over ocean swells)
    1) Not overheating with normal circulating return temps.
    2) Rebuilt the carburetors.
    3) Fresh fuel and fuel filter
    4) Swapped fuel tanks and hoses.
    5) New thermostat.
    6) New spark plugs
    7) Complete scheduled Honda service.
    8) New primer bulb
    9) New impeller

    The head Honda mechanic gave up, now the IT repair guy takes over and wants to replace the CDI Box now...ouch$$$
    I could sure use some help with this one...salmon season is passing me by
    Thanks Guys,
    Mike

  2. #2

    Default Re: BF25 loses power when under a load

    Does this only happen at full power? They surely would have checked the fuel pump?

    Have you tried squeezing the primer bulb when it starts to lose power. Does it improve the performance?

  3. #3

    Default Re: BF25 loses power when under a load

    Quote Originally Posted by Milgrip View Post
    Does this only happen at full power? They surely would have checked the fuel pump?

    Have you tried squeezing the primer bulb when it starts to lose power. Does it improve the performance?
    Thanks Milgrip for your reply.
    1). Yes the engine runs back only when it was been at full throttle for an extended period of time (30mins).
    2). Yes I tried squeezing the priming bulb the last time it lost power while trying to get back to the horbor.
    3). No the engine continued to loose power over a period of time (20mins) to the point I was unable to get my 14' Zodiac RIB on a plane.
    NOTE: The engine soundes fine even when I loose power. It just doesn't have any forward thrust! I will bring the throttle back down to an idle for say 15 secs take off again at 100% and runs normal for 30secs and then it will act up again.
    Honda seems to think maybe it's an electrical (CDI box) failure. That's an expensive guess on my part.
    Last edited by mikemanges; 09-11-2017 at 04:41 PM.

  4. #4

    Default Re: BF25 loses power when under a load

    This YouTube link shows my engine trouble in real time.

  5. #5
    Join Date
    Nov 2009
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    temecula, ca., usa
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    Default Re: BF25 loses power when under a load

    Is your oil pressure light on bright and steady while this is happening?
    I was thinking CDI too when I read your post. But make sure it's not a sender sending a false de-power signal first.

    And, ask your dealer if the new module doesn't solve the problem, will they take it back and return your money.

    If not, buy the module from boats.net and save a few bucks by replacing it yourself.

    Good luck.

  6. #6
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    Default Re: BF25 loses power when under a load

    Is your oil pressure light on bright and steady while this is happening?
    I was thinking CDI too when I read your post. But make sure it's not a sender sending a false sepower signal first.

    And, ask your dealer if the new module doesn't solve the problem, will they take it back and return your money.

    If not, buy the module from boats.net and save a few bucks by replacing it yourself. After all, it's plug and play so anyone can replace it.

    Good luck.

  7. #7

    Default Re: BF25 loses power when under a load

    The only Indicator light I have is on the tiller arm. As I understand it when the GREEN light is on things like (oil pressure and engine temp) are normal. I have never noticed the GREEN light ever change even when my engine looses power. That's not to say the engine isn't receiving a false signal though thus maybe a faulty module maybe. I asked about that possibility of false signals to the engine and got a lot of electrical jargon that I didn't understand.

    The shop is working under their repair warranty so they are obligated to make the needed repairs... I would think. But I'm starting to question their expertise.

    I will pass on what you have suggested and see what they say. It sounds like you might be on to something though.

    Thanks jgmo

  8. #8

    Default Re: BF25 loses power when under a load

    jgmo are you referring to a specific oil pressure 'module '? Is this module a sending component to the CDI box?

  9. #9
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    Default Re: BF25 loses power when under a load

    Hi mikemenges,
    No, the only module, per se', IS the CDI. Watching your YouTube video (excellent by the way) I do get the impression that the engine is going into the power de-rate mode. However, if it were doing so because of overheat, it should shut off after 20 seconds. If it were de-rating due to low oil pressure, you should see changes taking place with the green tiller light.

    But, what's happening COULD also be a fuel starvation issue. But you indicated squeezing the primer bulb while it's acting up makes no improvement and it should if it were a lack of fuel.

    What year is your outboard? Is it still under the 5 year Honda warranty? Or did you mean it's a shop guarantee agreement to fix the problem?

    If it's still under Honda's 5 year, I believe the CDI should be covered. But I'm not 100% sure.

    But I'm thinking CDI is getting to a given temperature under the hood and then begins malfunctioning. You could try running without the hood to see if that makes a difference. You could also take along a can of the computer "duster" compressed air and spray the CDI box to immediately cool it down and see what happens.

    If she runs with the cover off (secure It! They blow out sometimes) and doesn't act up it could be that she has an exhaust leak and that can cause this symptom too.

    Let us know what you find and
    Good luck.

  10. #10

    Default Re: BF25 loses power when under a load

    Hi jgmo
    I'm pretty sure my Honda BF25 is a 2004 model (BATJ-1000739).
    ••The mechanics have verified the motor is not overheating by using a infrared temperature reader while testing it on the lake.
    ••The fuel tanks and hoeses were swapped to eliminate a fuel delivery issue.
    ••The battery is 5years old. Could there be a charging issue?
    As far as the warranty goes, the Honda shop warents there work for 60days but the boat has been in and out four times during that time period. We are now entering the third month still not fixed. Guess I better get the warranty thing updated.

    Thanks jgmo
    I appreciate your input
    Last edited by mikemanges; 09-12-2017 at 01:36 PM.

  11. #11
    Join Date
    Jul 2017
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    San Diego, CA
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    37

    Default Re: BF25 loses power when under a load

    Just a wild uneducated guess, but could you be having fuel delivery issues with the new EPA ventless gas tank and demand valve? I would think squeezing the bulb would bypass that issue, but maybe not.

  12. #12

    Default Re: BF25 loses power when under a load

    Hi Solamar,
    No your input here is no more uneducated than I'm getting from the Honda Pros at the Honda Shop.
    Yes because my 6 gal fuel tank has no manual vent valve I've often wondered if the carburetors would be effected as the gas tank is drawn down without a means of equalizing it's internal pressure. Sometimes (if I can remember) I'll crack the gas cap to help prevent a negative pressure inside, but more times than not I forget and have never had an issue. I don't like doing that anyway fearing water could leak in the fuel tank.
    The short answer is I swapped fuel tanks with one that did have a vent valve from the Honda Shop and verified that wasn't the problem.

    Thank for your reply Solamar

  13. #13
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    Default Re: BF25 loses power when under a load

    I guess I will add my two cents......

    It does sound like fuel starvation but maybe it isn't.

    Has the dealer or you sprayed starting fluid or (propane....Jimmy) into the intake when the motor is failing to see if the engine picks up? If it picks up, then you know it is a fuel issue. If it does not, then it is time to look elsewhere.

    Has the dealer or you put a timing light on each spark plug wire and observed the light when it is failing? If there is a difference from one cylinder to the other, then spark is the culprit. That could mean cdi, coil/s, pulser, or even the exciter coil. The is time to put a peak reading voltmeter at the various locations before and after the cdi to see where the voltage is getting lost.

    If all that is good, it might be possible that the cdi is seeing the temperature sensor as an overheat even though it is not overheating. That is to say....a bad temp sensor. Normally, you would see an overheat light and hear an audible alarm. That does not seem to be happening, but then again, do your overheat light and audible alarm work as it should? I don't think there is an easy test for this.

    This appears to be heat related, however, has the dealer checked all the venting. Crankcase vent as well as carburetor vents and hoses?

    Lastly.....since the dealer and Honda seem to think that it may be the cdi, has they checked with their District Service Manager to see if he/she has a spark cdi for this motor that could be used as a test? I have done this a couple of times with mine, and fortunately, he had what I needed and it proved to be the cdi or ecm.

    The bad part about all of this, is that it takes 1/2 hour or so to get it to fail....unless they can get it to fail in a test tank, it is difficult to narrow down hanging on the back of a rib.

    I know.....more questions than answers. In one way or another, the dealer may have already done the above.

    Mike

  14. #14
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    Default Re: BF25 loses power when under a load

    By the way....that cdi is used on the 25 and 30 from 2004 to 2007 and through DK3 models. So, I would think someone in Honda land has a spare.

    Mike

  15. #15

    Default Re: BF25 loses power when under a load

    Awesome good to know. I'll find out tomorrow after the Honda mechanic tests my engine in Clear Lake CA. This will be the owner/repair service guru mechanic doing the on the water test. He told me today that "there is nothing wrong with my BF25 engine and everyone is full of ****". Been a long time someone said that to me.
    Thanks hondadude

  16. #16
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    Default Re: BF25 loses power when under a load

    I hope it fails for him. I hate it when I take a boat out and run it for what seems like forever, and I can not get it to fail.

    Mike

  17. #17
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    Default Re: BF25 loses power when under a load

    Well, that guy should have a look at the YouTube video you took. It shows it clearly slowing down in my opinion.

    If it does fail for him right away, try running it with hood off and see if there's a change.

    Good luck.

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