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  1. #1

    Default Honda BF50 Alarm Mystery

    I have late 90s BF50 (with controls) that has been giving me mysterious alarms for at least 6months. The alarms sometimes come & then go on their own. Other times i do something that seems to cure it, but then it eventually comes back. Nothing about these alarms is consistent. Its mostly a solid beep when in gear (and above idle), but ive also had it happen alot at idle & a few times even in neutral. Also, occasionally ive had an intermittent beep beep beep, but usually its solid. Sometimes the alarm wont start til ive been up on plane running for a little bit, but lately its often been sounding almost as soon as i put the boat in gear from startup.

    The first time this happened the momentary cure was to slow down off plane to 3000 rpm or less. Lately ive had to slow down all the way to a slow idle or sometimes neutral to make it stop temporarily. A few times it was opposite and would sound at trolling speed, but getting on plane would seem to make it stop. Also, im not certain about this, but the otherday it seemed i could make it stop if i adjusted the trim up slightly then all the way down.

    Adjustments that have seemed to make it go away for a longer period of time was a new battery. And another time, just putting an external charge on the battery. Howerever right now the battery is only a month old & rests at 13.5. When the motor is running it jumps up to about 14.5.

    I should also mention that the motor will usually eventually bog down if i keep running thru the buzzer. The time it takes to bog down is not at all consistent; sometimes quickly, but sometimes it doesnt bog.

    I pointed a heat gun at the motor and cant see anywhere its getting hot. Also, i tend to doubt it is because this beep often starts when the motor has only been running for a minute. I've only owned the boat 2 years and the temp & pressure lights have never been operational.

    Ok now heres the most confusing part. Today i disconnected (at the motor) the temp sensor wire, oil pressure wire, and the trim sensor. IT STILL BEEPED!?

    The only way i can permanently stop the alarm is by disconecting either of the two wires going into alarm itself under the console.

    I would take it to a mechanic, except i was told by one that this model is too old to be hooked up to the computer to identify the issue. So its gonna need to be figured out on the water thru trial and error.

    ANYBODY WITH ADVICE THAT CAN HELP ME SOLVE THIS IS MY HERO!

  2. #2
    Join Date
    Apr 2018
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    1,246

    Default Re: Honda BF50 Alarm Mystery

    You have a faulty trim gauge sender, your model sounded an alarm as described when the motor is tilted up and you try and accelerate. Disconnect the trim sender and bridge I think light green/blue and the black, if that doesn't work try other combinations, you will not harm anything, it's been a while so I am not positive on the colors. Alternatively, replace the trim sender unit.

  3. #3
    Join Date
    Apr 2018
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    1,246

    Default Re: Honda BF50 Alarm Mystery

    Just found the wiring diagram, I think it was orange and black.

  4. #4

    Default Re: Honda BF50 Alarm Mystery

    Quote Originally Posted by iang6766 View Post
    Just found the wiring diagram, I think it was orange and black.
    I thought it was yellow/green. If i'm right about the color, I alrwady tried disconecting the trim sensor & it didnt solve it.

  5. #5

    Default Re: Honda BF50 Alarm Mystery

    If you can fwd me the link to that wiring diagram, it'd be helpful.

  6. #6
    Join Date
    Apr 2018
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    1,246

    Default Re: Honda BF50 Alarm Mystery

    You can't just disconnect the sensor,you need to bridge the orange and black on the engine haness plug. The wiring diagram I have is a hard copy in one of my manuals so can't send a link.

  7. #7
    Join Date
    Apr 2018
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    1,246

    Default Re: Honda BF50 Alarm Mystery

    Engine harness plug that the trim sender plugs into

  8. #8

    Default Re: Honda BF50 Alarm Mystery

    Quote Originally Posted by iang6766 View Post
    You can't just disconnect the sensor,you need to bridge the orange and black on the engine haness plug. The wiring diagram I have is a hard copy in one of my manuals so can't send a link.
    Sorry im an electrical layman; can you explain what i need to do to "bridge"?

  9. #9
    Join Date
    Apr 2018
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    1,246

    Default Re: Honda BF50 Alarm Mystery

    Okay, disconnect the trim sender, then look at the 3 pin plug that you have disconnected it from and bridge the orange and black terminals inside the plug, alternatively you can leave the trim sensor plugged in, cut the harness to the sensor and bare and twist the orange and black wires together.

  10. #10

    Default Re: Honda BF50 Alarm Mystery

    Quote Originally Posted by iang6766 View Post
    Okay, disconnect the trim sender, then look at the 3 pin plug that you have disconnected it from and bridge the orange and black terminals inside the plug, alternatively you can leave the trim sensor plugged in, cut the harness to the sensor and bare and twist the orange and black wires together.
    Didnt solve the problem.

  11. #11
    Join Date
    Apr 2018
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    1,246

    Default Re: Honda BF50 Alarm Mystery

    Explain what you have done so far, there is nothing else on that engine that will cause the alarm you are experiencing , the other option is to remove the trim alarm module altogether.

  12. #12

    Default Re: Honda BF50 Alarm Mystery

    Quote Originally Posted by iang6766 View Post
    Explain what you have done so far, there is nothing else on that engine that will cause the alarm you are experiencing , the other option is to remove the trim alarm module altogether.
    I went pretty thoroughly into everything I've tried in my original post. I had the temp, pressure, & trim sensors all disconnected simealtaeosly & STILL had the alarm. Unless im somehow screwing that up, this must be some kind of faulty electrical issue, right?

  13. #13

    Default Re: Honda BF50 Alarm Mystery

    I dont want to lead you down the wrong direction with my suspicions, but I've put in a new battery twice in under a year & thats fixed the buzzer issue both times for a period of time. Either that is causing something computerized to reset or else there is some sort of voltage/charging or bad ground issue.

    These are just my guesses. & im not a very experienced handyman, so take them worth a grain of salt.

  14. #14

    Default Re: Honda BF50 Alarm Mystery

    Okay so i just took it out & got the buzzer sounding, then started disconnecting everything in that cross connect box. If I disconnect a specific 1 of the two white wires, the buzzer will go away. But if i try to increase rpms further, the motor still boggs down.

  15. #15

    Default Re: Honda BF50 Alarm Mystery

    Update: the white wire i disconected runs from regulator/rectifier. And the other end comes from the 15a fuse. Fuse is fine.

  16. #16
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
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    3,453

    Default Re: Honda BF50 Alarm Mystery

    Try running the engine at various rpm and use a DVOM to check for AC voltage leaking through the charging system. I don't know what the maximum allowed is for your system but I would suspect anything over 0.025 volts AC may be causing problems. Don't forget to set your meter to the AC volts scale and simply measure across your battery posts.
    Let us know what you find.

  17. #17

    Default Re: Honda BF50 Alarm Mystery

    Ok i set my meter to ACV 200. I was getting readings anywhere from 26-32. 31.5 was by far the most common

  18. #18
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
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    Default Re: Honda BF50 Alarm Mystery

    Well, it sure looks like you have way too much ac bleeding through the rectifier. BUT...and this is a pretty big one....

    .....I don't have enough knowledge or information as to what is acceptable for a bridge rectifier charging system. I was expecting a much lower voltage but I could be wrong.

    In my mind the rectifier should be converting ALL the AC volts from the charge coil to DC volts and the regulator should keep it at 14.5 vdc or under.

    It would be great if we could talk a forum member that has a 50 to measure theirs for comparison.

    ANYONE WITH A 50 hp want to help??

  19. #19
    Join Date
    Jul 2017
    Location
    meteghan, digby co, Nova Scotia Canada
    Posts
    17

    Default Re: Honda BF50 Alarm Mystery

    Your problem might be the small panel in the control box that might be shorted out due to salt water ,the one with the green light and overheat light.You might have to open up the box and disconnect this panel and retry the motor. Just a thought.

  20. #20

    Default Re: Honda BF50 Alarm Mystery

    Quote Originally Posted by Jimmy Robichaud View Post
    Your problem might be the small panel in the control box that might be shorted out due to salt water ,the one with the green light and overheat light.You might have to open up the box and disconnect this panel and retry the motor. Just a thought.
    !!!!!

    Okay i disconecres the the wires going into that indicayor light box.

    Dont want to declare premature victory, but it seems to solve the alarm issue.

    But is that mean that little light box is my issue? Or are we just indirectly disconnecting the alarm?

    The reason I ask is because with that box unplugged, my key did not work tk shut the motor off.

  21. #21

    Default Re: Honda BF50 Alarm Mystery

    Does anybody have the wiring diagram for a BF50?

    Still trying to figure out the root cause of this alarm.

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