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Honda BF2 w/ cracked flange on extension case

D

dmac

New member
I have a 2006 Honda BF2, 2HP 4 stroke outboard. Beneath the engine case, the extension tube is bolted to bottom of the engine by 3 bolts. At the top of the extension tube there's a cast ring with 3 flanges for the bolts. One of the flanges has a partial crack, about 1/2 way across. Is this a serious problem or if I don't do anything, what are the consequences?

I've removed the 3 screws holding the extension tube to the bottom of the engine/case. It is solid and does not move in the slightest (unbolted). The cracked flange is still holding together, but obviously weak. Before going further with this, I have a few questions,

From looking at the parts diagrams, the extension tube covers the exhaust and drive shaft, and supports the lower unit. Since the drive shaft is connected to the engine and the lower unit, is the shaft actually holding this together? How is the shaft mated with the engine? Do I need to remove the lower unit/shaft to get this apart

What is the best way to replace the extension tube? Is this just removing the lower unit, sliding the extension tube off, or do I have to take the engine/block assembly apart, to get the shaft out?

Is there a used part market where I could find a replacement extension tube?
Thanks,
Don
 
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Worst case is that the crack could ultimately break through and possibly the whole top of the extension case could break off and the engine would basically fall off. How likely is that to happen? No way to tell. A lot depends on how hard you run it.

The manual says to remove the engine and the exhaust before removing the extension case. I seems to me that you could remove the extension case with just removing those three bolts. The exhaust tube fits into a grommet down in the extension case and the vertical drive shaft is splined and fits into the bottom of the engine (actually the centrifugal clutch assembly). One or both of those may be somewhat stuck and they are probably holding the case on. A little wiggling may break it loose.

Honda probably suggests to remove the engine etc first, since it would probably be difficult to reassemble and get the exhaust inserted properly. Not sure on this. Maybe someone else has tried it. I normally have something on the engine to work on, so I have never had to take off the extension case before removing the engine.

Not being a welder, you might be able to find someone locally to "mend" the crack (not sure if it can be welded)...or check ebay or the web for a used one.

Mike
 
Mike, Thanks - it sounds like it is repairable.

Agree, if running hard or tossed by a wave into shore, the extension tube might break.

Is it correct that the engine is held on by the 4 bolts through the bottom plastic case? In my case, 2 are rusty and might be a problem. Does the entire engine lift off in one piece?

I think what I'm going to do is watch the crack for a while and see if completely breaks through or causes any problem. Will also keep my eye open for a replacement extension tube!
Thanks again,
Don
 
Don,

You are sort of correct….But first you have to remove the fuel tank, recoil starter, fan cover, choke rod, throttle wire from carburator, exhaust pipe, exmergency stop switch ground, THEN the four bolts.

Mike
 
Looking at parts diagram for Honda BF2 serial BZBF2201xxx and wanting to replace the extension tube - does anyone know the difference between these 2 parts:

15 04402-ZW6-010ZA SEE PART DETAILS - PRI; CASE KIT, EXTENSION *NH246* (LOOSY GRAY) (Honda Code 8976334). Use up to Frame SN 2205143.

15 04402-ZW6-000ZA SEE PART DETAILS - SUP; CASE KIT, EXTENSION *NH246* (LOOSY GRAY) (Honda Code 8580276). Use up to Frame SN 2205143.

Aside from different part numbers, one description says PRI vs. SUP. I have no idea which one to order.

Also, does include just the extension tube or all the parts enclosed by #15 (i.e, base, extension tube, tilting hardware...)?

Thanks again,
Don
 
SUP - is short for SUPercede. What I haven't figured out is the part the SUPerceding part (i.e. replaces the PRI) or is it SUPerceded, and the PRI replaces the SUP'd part. Maybe PRI means PRImary...or the original?

I think it's the former. If that's right, you'll want to order the part that says SUP. Someone else will nail this down and it will be useful info for all!
 
freeportd said:
SUP - is short for SUPercede. What I haven't figured out is the part the SUPerceding part (i.e. replaces the PRI) or is it SUPerceded, and the PRI replaces the SUP'd part. Maybe PRI means PRImary...or the original?

I think it's the former. If that's right, you'll want to order the part that says SUP. Someone else will nail this down and it will be useful info for all!
Click to expand...

It is confusing. I think it is the latter - another parts website has the 04402-ZW6-010ZA SEE PART DETAILS - PRI and the current part number.

I also verified that the assembly includes all the parts enclosed in the diagram. That would be a new base, tilt/lift mechanism....

Now to see if I can get the 4 rusted bolts from the bottom of the base.

Don
 
A couple more questions - I was able to remove the set of bolts holding the extension tube and engine, etc. he heads where rusted, but bolts themselves fine. When reassembling, should I use some sort of anti-seize or locktight on the threads? I appreciate everyone's help - this gives me the confidence to replace the extension tube!
Don
 
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I would retap the threads to clean them up. And clean the rust off of the bolts.

Using blue loctite (252), will help keep them in place, but more importantly seal off corrosion. If you use antisieze, make sure that the base of the head of the bolt is clean and dry of antisieze or oil. You need the friction of the bolt head being held against the motor to keep it in place. Be sure to torque per the manual.

While you have all that apart, be sure to inspect the centrifugal clutch for rust/corrosion etc. If it or its bearing are rusty...now would be the time to replace them. The clutch outer assembly, comes with the bearing. Change the associated small seal that is in the clutch housing. If the bearing seems smooth, you might be able to clean off the outer clutch assy with some steel wool...as long as it is not pitted, etc.

I know TMI (Too much information)

Mike
 
Mike,
I appreciate the info - the more the better! I found the torque specs and printed the assembly pages from the repair manual. I should be good to go in replacing the extension tube.
Don
 
FWIW, an update,

Following the pages in the service manual, I was able to disassemble, clean and partially reassemble the engine. A $1.04 part prevented me from completing the reassembly! The "pin dowel 8x14" between the extension tube and lower unit was corroded and I was unable to remove it from the base of the extension tube. Also, in reassembling the lower bushing, it seems that the exhaust tube is not held tight and seems very loose. Inside the bushing are ridges, but they don't seem to be grip the exhaust tube. I'm concerned that this might allow water to seep into the tube. When ordering the pin-dowel, to be safe, I'm going to order a replacement lower bushing too.

Now that I feel pretty comfortable that I can put this back together, I'll measure the wear on the clutch and double-check the clutch surfaces. It looked more than 1mm, so I think I'm OK here. The engine shows very little signs of use/abuse, so the clutch and bearing should be OK.

The only other surprise was a breather tube on the clutch housing. It took me a while to find the service manual update that shows how this rides behind a plate on the front of the engine.

One last question, I have automotive lithium grease - is this usable or do I need marine specific grease? The grease on the old parts seems heavier than what I have.

Now to wait for more parts! Thanks again,
Don
 
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