Rapid corrosion on motor

Sea Chaser

Crew 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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have you checked to ensure your zinc's are installed properly.
Is there excessive corrosion on your zincs
That should not be happening
 
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.
 
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.
 
Sorry, I was a Honda owner and speak from experience.
they can be welded, although it usually splits again
in another place.
 
Sorry, I was a Honda owner and speak from experience.
they can be welded, although it usually splits again
in another place.
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.
 
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?
 
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?
Yes,I think so too,I have a 2006 225, moored 6 month a year and not sign of corosion
 
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?
Fibreglass
 
Yes,I think so too,I have a 2006 225, moored 6 month a year and not sign of corosion
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).
 
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).
Corroded ground wire??? I pull all my wire off and clean all connections every winter, pain in the butt 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
 
Corroded ground wire??? I pull all my wire off and clean all connections every winter, pain in the butt 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
I’ll be sure to go over everything .
 
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.
 
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.
 
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.
 
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