Cutting Off a Flywheel? 1974 Johnson 4HP

[Doolin]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

>>Just run your torch in a circle maybe 1/2" away from the crank, make sure you have the puller on it with plenty of pull. At some point, it will pop off. Two minutes isn't nearly enough time and I doubt you need to worry about melting it.


Thanks... I'll try that next.

 

[Doolin]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

>>I just thought. you have a flywheel cracked out at the center hole, Do you know someone with a lathe to make you a centered bushing to slip over the crank shaft

It's the crank itself that cracked. The last few threads shattered. I think I can grind off that much and be ok.

I did drill in the flywheel along the crank at the suggestion above but I think I can tap that and 'red locktite' a bolt in place and grind it flush to fill that hole once I get it off.

 

[R.Johnson]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

The bolts' you need are part #307641, For the bigger engines part#309492, The washer's are #307639.

 

[Doolin]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

I used the 'blue wrench' with the puller in place. The bottle ran out after only about 5 minutes... so I'll get a new one and try again.

I ordered the bolts (not cheap... about $30 for 6 bolts and 3 washers). When they show up, I'll drill 3 new holes offset between the original ones (with busted off grade 8 bolts in them), tap them and try with the 'shouldered' bolts.

 

[lowkee]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

Just a thought, as I haven't seen it mentioned.

When you have the puller REALLY tight, take a hammer and bang on the center bolt. You may wish to try holding a lever (pry bar or large screwdriver) under the flywheel with some decent muscle (but not so much as to break the flywheel) while banging with the hammer. The theory behind this method is to simulate how an impact drive works. You have the torque applied by the puller and the pry bar and the impact jarring action of the hammer on that center puller bolt. Do that after heating just around the crankshaft (warm the flywheel, not the shaft, and not to 500 degrees, just barely hot, certainly not red hot). It won't be a bad idea to spray some PB blaster on the threads about an hour before you try this.

That is pretty much the method I use when a flywheel is being TRULY stubborn. I have yet to break or get beaten by any flywheel, which is saying a lot for the # I have removed (easily high 100's).

 

[Doolin]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

I had the same thought (pounding on the center bolt) but wasn't sure if it was such a great idea (since it was me guessing and not based on what anyone else had tried)

I've got the new propane bottle to heat with, I've got the 'shouldered bolts' on order and it's had penetrant applied very many times for about a week.

I'll keep the puller on it with pressure and penetrant until the bolts show up. Then I'll try the new bolts, heat, good pressure on the puller, some upward pryforce and pounding the center bolt.

Then... if that doesn't work... I'm going to cut it off

 

[lowkee]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

If all of that doesn't work, there are two options left:

A: Use the motor as target practice, since it is obviously a motor from hell
B: Post it on craigslist with a title of "Runs great, just needs a starter"

or..

C: Do A:, then B:

 

[Doolin]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

That's funny

I've had the Craig's List thing done to me... I think I can save someone the headache

I do have a serious need to beat this motor though... and while 'beating it' into a million tiny pieces would definetly provide some level of satisfaction... for me to win... it has to be my slave an push my boat around

 

[lowkee]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

Any update? How did it go? I haven't seen it posted on CL yet.. that is a good sign.

 

[jonesg]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

They're a tough sell on crazedlist with bullet holes in the block.

 

[Doolin]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP



The 'shouldered stripper bolts' are on order and on the way, but not here yet.

They should give me the best pulling power possible. It's had several weeks of penetrating lube now... and several minutes of 'blue wrench'.

I've got a new bottle of propane... so, I'm pretty much ready to give it 'the final go' when the bolts show up.

 

[R.Johnson]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

If that crankshaft is split out, you need to do something about that. That's why I asked about a centered bushing. That center bolt need's something strong, and stable to push again'st.

 

[wilde1j]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

Boy, at this point I think I'd try dynamite!

 

[R.Johnson]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

The proper puller,and bolt's would have saved all this?

 

[Doolin]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

>>If that crankshaft is split out, you need to do something about that. That's why I asked about a centered bushing. That center bolt need's something strong, and stable to push against.


The puller set I have has two 'centering adapters'. The first one, which was the one I used first is cone shaped with a point which nicely centered the puller main bolt on the crank end. Unfortunately, the cone split the crank before the flywheel let go.

The second adapter is negatively hemispherical. That's the one I switched to when the crank split. It may not be perfect... but the alignment looks good and it looks to be making good contact with the crank.

>>Boy, at this point I think I'd try dynamite!
Similar thoughts have crossed my mind... but usually not with the intent of cleanly removing the flywheel


>>The proper puller,and bolt's would have saved all this?
Maybe. The puller is probably not an issue... any harmonic balancer puller is probably fine. At the suggestion of users here, I used 1/4 X 20 grade 8 bolts. These are about the strongest grade of 'normal' bolts. They twisted and snapped. The 'shouldered stripper bolts' suggested above have a shaft that's much thicker than the normal bolt which is 1/4" all the way up. The thread section is 1/4 inch, then the threads end at the 'shoulder' where the bolt shaft is thicker. When the threads are sunk all the way in... the 'shoulder' is pulled flat against the flywheel. This helps to prevent the twist that was part of the problem with the grade 8 bolts. The shaft being much thicker should also be much stronger. The second part of my problem was the standard 'thick' washer that I used, still started to pull down through the harmonic balancer puller which caused some of the twist in the grade 8 bolts. The hardened washers I ordered should prevent that. So, not a guarantee that it'll work but it should provide me with the greatest amount of pull possible.

And of course if that doesn't work... I'm really looking forward to at least the limited amount of destruction that my grinder will do when... cutting it off

 

[osceola328]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

I had the same problem on a 200hp that I was able to break loose this weekend after 3 LONG weeks of trying. Just as lowkee was saying above, I was able to get it to break by using the puller to apply lots of pressure (torqued as much as I could with a 2' breaker bar) and I took a piece of 2x4 and tapped the bottom of the flywheel. (wood used to prevent breaking teeth on flywheel) I had to knock it pretty hard but it finally popped off of the key that holds it in place.

Hope that helps...

 

[Sea18Horse]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

Just to add to the discussion, When you rap on the end of the puller with a hammer you must hold up on the flywheel while doing so. If you lift up on the flywheel you will notice a small amount of up and down play. You need to lift it until it's at the top end of this play. If you just pound away on the center bolt you are applying all that force directly to the thrust bearing. And you must move the mass of the entire engine or deform the thrust bearing in order to apply any force to the crankshaft/flywheel joint. If you lift up on it then you take that force off of the thrust bearing and you only have to move the mass of the crankshaft itself. Never pound on a thrust bearing if you can help it!

Also I don't see mention of it but you want to leave the nut on the end of the crankshaft so that the flywheel doesn't go flying off when it finally does pop.

Cheers...................Todd

 

[jesseoshea]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

I spent about 12 hours on my Johnson 120 flywheel using all of the conventional methods and a few that I'm not proud of. lol I was finally able to get it off after leaving tension on it for 3 days while it was also soaking with pb blaster (tension applied with harmonic balancer puller tightened with 1/2" impact). I was finally fed up and heated it with a propane torch. After getting it reasonably hot (not too hot to damage the seal or any other part) I had a friend with a pry bar applying more tension on it on one side of the flywheel while i was on the other tapping the flywheel up with a 2x4 and a 2lb hammer. The harmonic balancer puller was still applying tension while I was tapping on it. It finally "popped." No damage was done to the flywheel, crank, seal or others.

Goodluck!

 

[karlow1]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

I would add just one thing. You have it all loaded up with the puller, lubed up and you have tried hitting it a bit with a hammer to make it ring. What did the job for me was to pry it up a bit , rotate it 90 degrees and repeat. I was prying along the edge using the case and a block as a fulcrum. Then boom she popped up about an inch. I never added much heat. Remember the first rule, do no harm! A little late for that one but remember, do not bend the fly wheel. FYI, you have a lot of thermal mass to work with. If you add heat with a single propane torch, you are not likely to be able to damage the flywheel, just the paint, seals and electronics.

Put down that hammer and back away slowly

It is always best practice to stop have a cold one and work on it tomorrow.
That way you brake less stuff.

KP

 

[Doolin]

Re: Cutting Off a Flywheel? 1974 Johnson 4HP

WOW (12 hours on my Johnson 120 flywheel).

I wonder if I can get my 6' iron digging pole wedged in there

The shouldered stripper bolts and washers arrived today. I'm a little surprised in that the length of the threaded portion of the bolt is only about 1/2". I'm now concerned about the threads ripping out with only half the 'thread count' to hold onto compared to the 1"+ threaded portion on the standard grade 8 bolts.

I'm not concerned about these breaking though... they look REALLY strong.


I think you're right about 'taking the night off' when things aren't going right. I can get frustrated and decide on the 'next step' before I think about all the possible steps. A good night's sleep often leads to a 'better' option

More updates once I get these bolts pulling.