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bf100 How to separate crankshaft from vertical shaft

rocknroj

Contributing Member
Good Day,

The title says it all. First time project for me. Seems I cannot pull the powerhead with the vertical shaft connected. Think its the bushing.

My thoughts.. Need someway or something that I can get to grip the vertical shaft well enough to survive some hammer blows. I am guessing the crank and downshaft are stuck together at the splines... Probably never been apart.

I need to do a couple of these as I piece 2 motors into one..

Any ideas or experience appreciated.. I have a couple manuals but the finer points of working on an old engine are never covered..

TIA... Thanks in advance for your thoughtful replies....
 
I'm not sure if I completely understand what you're trying to do but the mainshaft should simply slide out of the crankshaft when you remove the gearcase assembly. The mainshaft and shift rod come away with the gearcase as an assembly. After the shaft and gearcase are clear you can then unbolt the extension case to access the bolts that hold the powerhead to the oil case. That's how I've disassembled them anyway.

I've never seen a mainshaft siezed to the crankshaft spline but I suppose it could happen due to corrosion. If that's what you're up against you will need to find a way to get some PB Blaster or Aero Kroil (better) up in there and then give it time to work.

I would urge you not to use force against these components as they are fragile and, for the most part, unavailable new anymore. Although, what you can still buy is typically so expensive I wouldn't want to pay for them anyway. Patience is key when working with these old outboards.

Good luck.
 
Not sure if it shows but I have the case mounting bolts out and I can move case around but cannot lift it out.. I cannot really see that seal around the driveshaft nor can I get a good idea about how it fits from the schematics. I am guessing that seal is holding the engine block from lifting out of that lower housing/oil pan.. I think the seal is NLA

One pic shows the hole in the cylinder wall from a few years of salt. Tha'ts despite regular flushing..

I have another parts motor that I was planning to use to piece together another runner. The motor in question ran fine until the water started leaking..

These are nice little motors for the most part and super reliable. I think getting them hot enough to get a good flush after the salt exposure is a bit of a problem though.

I may put one together sans thermostat and see how that goes.. Generally mine gets run all day for trolling once I hit my spot.

Around here most of the used units are most likely near death from the salt. (puget sound)
 
Ok, the first pic says it all....

Yes, the splines must be rusted up in there.

All I can tell you is to buy some Aero Kroil (the oil that creeps) and get it in there. Turn the whole thing upside down and spray it in there so gravity will help it go into the "cup" of the joint.

Apply it as often as you think you need to. That stuff DOES creep and will eventually break down the corrosion but it takes time to work. I've left it on seized shaft splines for weeks trying it every few days. When the parts finally came loose you could then see how the oil had slowly worked it's way in there.

Just remember that if you get in a hurry and start pounding on it with a slide hammer or something you will run the risk of destroying the bearings, thrust washers and seals. Not to mention possibly boogering up the crankshaft.

You might speed things up a bit by heating the end of the shaft with a legitimate heat gun. Heat helps the penetrant work its way in. But I wouldn't recommend using a torch and you should even use lots of caution using the heat gun. Although I'm pretty sure that the lower oil seal is still available if you melt it. The upper one isn't anymore.

Best of luck with it.
 
Guess I will need to do that. Did some looking and found some pics of the shaft, used parts for sale on e-bay. Looks like it has a shoulder near the top and a seal (part 91255-881-004) that would fit around the shaft and into the oil case. So I am guessing that shaft won't slide up past the shoulder and needs to come off before the block can be lifted... Is that correct?

It does appear that the seal can be had for about $15.. Looks like The crankshaft splines slide into the driveshaft from the top so getting penetrant in there from the top would be difficult and would have to come from the oil case.

Maybe I can find some with long straw.. not sure if I can get a peek in there with the scope but I do have some play between the block and the oil case so I will check it out
 
Well, as I said, this is a unique problem to me but I believe you are correct about the shaft not passing through the oil case still attached to the crankshaft. I don't have an example to reference and I haven't done a ton of these. I've always just pulled the shaft out from the bottom. I guess I've been lucky not to encounter this problem before.

I do know that I've never replaced the "coupling seal" (91255-881-004) you listed. Maybe I should have since that is probably what allowed water up into that spline. I believe that there was another guy here on the forum that had the same issue but I don't recall how that turned out. I will peruse the archives and see if I can find that thread.

As far as getting the KROIL in there, I have used a piece of appropriate diameter model plane engine fuel line slipped over a shortened section of the delivery straw that comes with spray can to get some reach and flexibility for hard access places. It can be frustrating because it's hard to aim and control but it might help. You can also insert another piece of straw in the free end to gain some accuracy and, sometimes, extra long hemostats can help too. If you can work with the whole affair upside down then just getting some on to the shaft will allow gravity to carry it down and into the coupling. It falls under the "hold your tongue just so" heading.

Just keep in mind that oil case is pretty brittle and is easily cracked and broken. I know that one from experience.

I hope this turns out well for you but it's going to be a "patience tester" I'm afraid.
 
Well, I found one post where the guy said that he got the block and vertical shaft out from the oil case but the shaft was still stuck He didn't explain how he accomplished that and I didn't think to ask. He was in Norway and I was already cringing about how he was going about things using some degree of force.

He never came back with what happened and I was probably having some very serious spinal surgery about then and lost interest. But it does indicate that there may be a way to get the oil case out of the way. Just guessing but it may involve forcing that coupling seal out of the case along with the shaft.

It does appear, from the parts page illustration, that the seal installs from the top so, if that's what has the shaft trapped, it might be doable. I will go through my shop manual and see if there's anything definitive about installing it.

But be very careful if you pursue that course of action.

The thread is:
dated 2011
His handle or username was tropax

If you want to read the thread or try to PM him go to:
Search Forums (blue button in upper right corner of forum home screen)
Type in key words.... stuck shaft honda
Press "search now"
Scroll down to title:
bf100b (pre 97)
It's about ten titles down.
 
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I found nothing in the shop manual about that seal. But one thing I've noticed that is fairly consistent about the Honda parts illustrations is that they will often accurately indicate how a given part is attached. It's not something I would bet the ranch on but the seal does appear to be installed from the top of the oil case and it would seem to exit from the top as a result.

Good luck.
 
Thanks much. Found the post you refer to. Looks like the same problem as mine. Gonna do the soak thing. I have time. Did that on some other parts and indeed took quite some time and patience.

I will post back my success when done and a couple pics.

Ever run one of these without the thermostat?

Salt destroyed the cooling jackets, so I think without a stat I could at least get an effective flush when done.

I am guessing it would be ok, just take a bit longer to warm up....

thanks again.
 
There's a technical "catch" associated with running most engines without thermostats other than slow warm up but it's directly associated with it.

The stat facilitates warm up by controlling a bypass circuit between the head and block, right? That allows heat from the head to bypass the outlet in this case and get recirculated back into the block. When the thermostat gets warm it starts preventing that recirculation and will eventually stop it from happening.

If you leave the thermostat out, that bypass stays open and the recirculation of pre-heated water happens all the time. This means that, under high heat, high load conditions, the engine could actually overheat with the thermostat removed.

That and the fact that these engines are famous for "making oil" when run cold all the time makes me not want to endorse leaving the stat out.

But....I'm positive that it's done a lot! So, being armed with the information about the effects and consequences, you can decide if that's what you want to do.

Good luck and looking forward to your SUCCESS post.
 
Got it disassembled. Purchased what is called a shaft collar with a 1" inside diameter. It clamps tight to the shaft with an allen wrench. These are generic bits that are available in various sizes. Then a sharp wack with a hammer and out it comes. Almost impossible to get any penatrating oil in there and in fact in spite of my best efforts totally dry inside. The real trick is finding something that can get a grip on the round shaft. Didn't know what a shaft collar was before this.shaft collar.JPG
 
Well, I suppose that, if we were machinists, we might have known about those. I have threatened many times to become one but always got distracted. Good find and congratulations on the deployment to solve the problem.

Were there signs of corrosion bonding or a clear indication of why it was so badly stuck? My experience is that they usually just come right out with little effort.

Thank you for the update, photos and explanation on how you succeeded!
 
Not much corrosion. A bit of rust. Enough to hold the splines together. Just impossible to get a good purchase on a round shaft without the above pieces. Plenty of u tube vids of guys struggling with the same and trying various methods, multiple clamps of various types etc. If the clamp slips at all then the force of the blow becomes clamp movement instead of downward force to free the splines. It only took a light blow to knock it loose.

I took 3 of these engines apart and this is the only one that stuck. The honda repair manual clearly states to apply grease on assembly . This was completely dry. The ones that came apart easily were done by the book, this one not. Good reason to buy a service manual and follow the procedures. Its a well spent $50.
 
Couldn't agree more about getting the service manual before "digging in"

Even though these are very simple outboards, there are still some fine points in the manual that can be easily overlooked without it.

While it's my opinion that the manual could have been more complete and better organized it is still a very good investment IF one is willing to sit down and go through the info it provides.

Thanks again for your observations and summary. Good stuff!
 
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