Rapid corrosion on motor

Discussion in 'Boats, Motors, Trailers and Towing Rigs Forum' started by Jon, Sep 17, 2020.

  1. Jon

    Jon Active Member

    Honda BF 90 outboard lower unit starting to rapidly corrode. Not sure what I’m doing wrong or what is going on? Rinsed , flushed cleaned after every use. Zincs all look good . Little bit corroded I think I’ll be changing them just to make sure. Any suggestions gladly accepted
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  2. gone fishin

    gone fishin Active Member

    have you checked to ensure your zinc's are installed properly.
    Is there excessive corrosion on your zincs
    That should not be happening
     
  3. Jon

    Jon Active Member

    Yah zincs look ok to me. Gonna change them out regardless now. It’s happening at an alarming rate too.
     
    Lucky Streak likes this.
  4. profisher

    profisher Well-Known Member

    Is your boat moored or on a trailer? I would be looking for voltage leak from your boat if on a trailer or from the docks if moored.
     
  5. Jon

    Jon Active Member

    Yah it’s on trailer. Any tips on looking for a voltage leak?
     
  6. scott craven

    scott craven Well-Known Member

    Honda's are bad for corrosion, the next place to watch is your prop shaft housing.
    corrosion builds up internally and will eventually split the gear case.
     
  7. Jon

    Jon Active Member

    :(
     
  8. scott craven

    scott craven Well-Known Member

    Sorry, I was a Honda owner and speak from experience.
    they can be welded, although it usually splits again
    in another place.
     
  9. Jon

    Jon Active Member

    Did your motor look like that? Seems very excessive and rapidly comming on . I’m gonna check for voltage leaks and check wiring over the weekend . Most likely change out zincs too.
     
  10. chris73

    chris73 Well-Known Member

    And buy the correct zinc alloy, zinc is not always just zinc.
     
  11. profisher

    profisher Well-Known Member

    Honda's don;t have the internal water passage protection like Yamaha but this is more external. For a motor that is only in the water during use and then rinsed.....while it sits most of its time on a trailer...there has to be something strange going on....like voltage leak. Is it on a glass or aluminum boat?
     
    brutus likes this.
  12. brutus

    brutus Well-Known Member

    Yes,I think so too,I have a 2006 225, moored 6 month a year and not sign of corosion
     
  13. Jon

    Jon Active Member

    Fibreglass
     
  14. Jon

    Jon Active Member

    Yah frustrating to say the least. Looks like it’s been repaired in the past as paint doesn’t match the rest of the motor. Gonna dig into this voltage leak theory this weekend for sure. Been reading up a bit and seems like what is happening . Not sure how it’s all of a sudden happening though. Nothing has been changed since I purchased it (used).
     
  15. brutus

    brutus Well-Known Member

    Corroded ground wire??? I pull all my wire off and clean all connections every winter, pain in the ass and time consuming but never have electrical issues with anything, I always make sure I replace butt ends that are moldy, wires and bus bars , basically go trough all conections
     
    Jon likes this.
  16. Jon

    Jon Active Member

    I’ll be sure to go over everything .
     
    brutus likes this.
  17. profisher

    profisher Well-Known Member

    I noticed the miss colour match in paint....so it could be that there was corrosion there hidden by paint by a previous owner..sanded or ground flush to blend in. But just like any rust if you don't cut it out it just comes back...starts by bubbling the paint...and then comes back full on quite quickly. Might just be what is going on here.
     
  18. gungadin

    gungadin Well-Known Member

    Number of things come to mind. The lower unit may be an aftermarket one, pehaps with a different alloy. Zincs only protect if they are not insulated from the metal they are attached to. in other words if any substance is between the zinc and the motor the zinc will be unable to act as an anode. As Brutus says a corroded ground wire could cause your problems. As the corrossion is taking place only on the leg I would look at the trim tab just above the propeller. The paint on the leg may be of a type that is not compatible with salt water and could cause the aluminium to erode.
     
  19. Pineapple Express

    Pineapple Express Well-Known Member

    Check all the wiring harnesses on the motor and between the motor and the battery. If you've had a sudden change in the corrosion of the motor then you've had a change in the electrical charge on the motor. The comments from @gungadin and others are good, but I think if this is a sudden change you've gotta look at the boat electrical system.
     
    ericl and brutus like this.
  20. Macfuzza

    Macfuzza New Member

    Needs a sand, primer and paint job at least.
     

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