Logo

Workaround for Honda BF90 Water seeping up the vertical shaft into Flywheel case?

cwproeco

New member
Yesterday I replied to an old thread with below. jgmo suggested I open a new thread so more people would see it. Thanks jgmo and lang6766 for quick responses.

Hi All,
I have been gifted a BF90 with the water intrusion problem up the vertical shaft and into the flywheel area. Starter bendix gets corroded and stops dropping low enough to engage w/ teeth on the flywheel. Otherwise, the engine runs great. Taking off the powerhead and replacing the seals seems like way too much of an investment for a 10 year old engine and the likelihood of breaking something in the process reasonably high, so I'm looking for a workaround. Has anyone tried drilling a drain hole in the flywheel housing below the flywheel so it never gets up to the starter or does the water come-in above the flywheel and spray around?
Any good ideas welcome!
Chris
 
See my answer in your original post on the other thread

I'm dusting this thread off after all these years to try to consolidate this solution, and get in a question of my own. I have 2001 Honda BF90A that has a big problem with water intrusion into the flywheel cavity. I run in salt water. So my last starter motor lasted 2-3 months before loading up with corrosion and guck. First, the promising solution supplied by iang6766 in 2018:

"I have a permanent fix for this. First, make sure all the moisture is out of the flywheel housing, coat everything a best as possible with some form of corrosion guard. Then ensure your water pump is in good condition. With the lower unit off, drill two 10mm holes into the bottom of the extension housing, either side of the shift shaft directly above where the water pump sits when the lower is back on. This will allow any water leakage from the pump to drain out before it fills the whole extension housing forcing its way past the mount case seals. This method is also a good preventative measure which I have used with great success on all the older BF 75/ 90 motors."

So here are my questions:

1. The attached photo shows my engine with potential hole locations shown in red. Are these locations appropriate?
2. How is the water likely getting into the extension cavity (above the separator flange and below the flywheel cavity)? Are the seals in the cooling tube leaking? My tell tale flow seems fine, but I could be losing some flow from the pump and not really noticing it

Thank you in advance. Any other responses or experiences would also be greatly appreciated.
 

Attachments

  • IMG_3702a.jpg
    IMG_3702a.jpg
    133 KB · Views: 139
  • Screenshot 2025-03-26 212633.jpg
    Screenshot 2025-03-26 212633.jpg
    80.8 KB · Views: 172
I'm dusting this thread off after all these years to try to consolidate this solution, and get in a question of my own. I have 2001 Honda BF90A that has a big problem with water intrusion into the flywheel cavity. I run in salt water. So my last starter motor lasted 2-3 months before loading up with corrosion and guck. First, the promising solution supplied by iang6766 in 2018:

"I have a permanent fix for this. First, make sure all the moisture is out of the flywheel housing, coat everything a best as possible with some form of corrosion guard. Then ensure your water pump is in good condition. With the lower unit off, drill two 10mm holes into the bottom of the extension housing, either side of the shift shaft directly above where the water pump sits when the lower is back on. This will allow any water leakage from the pump to drain out before it fills the whole extension housing forcing its way past the mount case seals. This method is also a good preventative measure which I have used with great success on all the older BF 75/ 90 motors."

So here are my questions:

1. The attached photo shows my engine with potential hole locations shown in red. Are these locations appropriate?
2. How is the water likely getting into the extension cavity (above the separator flange and below the flywheel cavity)? Are the seals in the cooling tube leaking? My tell tale flow seems fine, but I could be losing some flow from the pump and not really noticing it

Thank you in advance. Any other responses or experiences would also be greatly appreciated.
Did you ever do this and was that the right location?
How well did it work out?
 
Trust me it works, done it to a lot of motors. If your flywheel is badly rusted, then your crank will be too. In that case you will need to remove the powerhead to clean everything propely as well as replace the seals
 
Back
Top