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Need Honda guru: model year interchangeability lower unit BF90A

L

lund_prosport

New member
Hello all,

I have a 1997 BF90A BBBL that needs a new lower unit.

I tried to follow the part number history of supercedes/obsolescence myself, and with a guy on the phone from Honda Marine, to no avail. The guy on the phone at Honda couldn't come up with an active part number that can be ordered, and is documented to fit the 1997 motor.

I can find a 2005 or 2006 lower unit. Can I use the newer item on the 1997 motor?
 
You can use the newer gearcase (for the carbureted 75/90's) but you need to change the shift rod and thrust washer, etc.

You do not need to take the new gear case apart.


1 Shift rod A 24320-ZW1-B00
1 Washer, propeller thrust 90506-ZW1-B00
1 Washer, plain (18.5 mm) 90508-ZW1-B00
1 Nut, castle (18 90301-ZW1-B00
1 Pin, split (4.0) 90758-ZW1-B00


The older gearcase was a Mercury gearcase and the splines on the shift shaft at the gearcase were different than the newer 90's. The propshaft chamfer was also different. That is why you need a new thrust washer, etc.

Mike
 
hondadude said:
You can use the newer gearcase (for the carbureted 75/90's) but you need to change the shift rod and thrust washer, etc.You do not need to take the new gear case apart.1 Shift rod A 24320-ZW1-B00 1 Washer, propeller thrust 90506-ZW1-B00 1 Washer, plain (18.5 mm) 90508-ZW1-B00 1 Nut, castle (18 90301-ZW1-B00 1 Pin, split (4.0) 90758-ZW1-B00 The older gearcase was a Mercury gearcase and the splines on the shift shaft at the gearcase were different than the newer 90's. The propshaft chamfer was also different. That is why you need a new thrust washer, etc.Mike
Click to expand...
Mike, thank you! Can I use my old shift rod and thrust washer from my old 1997 unit?What year did Honda use Mercury lower units?BJ
 
Honda used the Mercury gearcase through 1998. On or about 1999 is when they changed.

If the info that you provided is correct, you will need the additional parts that I listed.

Mike
 
Great thread! I'm in the same boat with a 1997 Honda 90hp and this gives me more options for replacement units since they are hard to come by. Can I assume that the prop from the Mercury lower unit fits the Honda 1999-2006 lower units? How difficult is it to replace the shift shaft? Thanks!
 
Yes the prop fits. I am using my old 1997 prop which was on the newer Merc lower unit.

The shift shaft is not hard to replace, if you have average or above average mechanic's skills. It needs to be properly oriented, that is not a big deal. The tricky step is to fit a circlip to the top of the shaft, where it meets the power unit. Patience and small fingers are helpful. It took me 2 or 3 tries but I eventually got it.
 
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