Author Topic: Machinists please step in..way off topic  (Read 2451 times)

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djburton

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Machinists please step in..way off topic
« on: September 03, 2021, 08:54:11 AM »
I apologize in advance for being off topic but here goes. The subject is a 200 hp Mercury outboard.It developed a really bad knock at idle but ran great a speed.I continued to run it because of a tight tournament schedule It took me quite a while to figure it out but it ended up being a loose flywheel. Anyway,I tightened it up and it was ok for a while but came loose again.This continued to happen quite frequently.The flywheel is on the tapered keyed top end of the crank.I bought a new flywheel,washer and nut,coated everything with red Loc Tite and the problem disappeared for a year or so but now it's back.Apparently the taper on the end of the crank is somewhat compromised. The question....Is there any type of compound or other method I could use to tighten this connection? Boat guys have nothing to add except a new crank.I know there are a bunch of brilliants minds on here and am hoping someone can help.   Thanks!

Heo

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Re: Machinists please step in..way off topic
« Reply #1 on: September 03, 2021, 09:27:20 AM »
if its not to bad lapp the crank and fltwheel togetter with
valvelapping compound



The defenition of a Gentleman, is a man that can play the accordion.But dont do it

machoneman

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Re: Machinists please step in..way off topic
« Reply #2 on: September 03, 2021, 09:44:01 AM »
No machinist here but....I'd get some Prussian Blue or other marking compound and give that 'wheel a few spins first to see exactly where the mismatch may be, especially if the downside of the 'wheel may not sit square to the crank flange. 
Bob Maag

RJP

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Re: Machinists please step in..way off topic
« Reply #3 on: September 03, 2021, 01:22:11 PM »
if its not to bad lapp the crank and fltwheel togetter with
valvelapping compound
Heo nailed it. try the lapping compound.

70tp

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Re: Machinists please step in..way off topic
« Reply #4 on: September 03, 2021, 01:23:52 PM »
Valve lapping compound as said above.  On our blower Briggs n Stratton’s it had to be done to keep the flywheel key intact above 15 psi.    MAkes big difference.    Start with course then use fine.   Don’t put a hardened key in it.  It will peel a chunk of crank out.   Lap it then blue it to confirm fit

allrightmike

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Re: Machinists please step in..way off topic
« Reply #5 on: September 03, 2021, 03:59:02 PM »
If the keyway is compromised will anything hold for long?

WConley

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Re: Machinists please step in..way off topic
« Reply #6 on: September 03, 2021, 04:39:53 PM »
I imagine the keyway is buggered up a bit on both the crank and flywheel.  Replace the key if it is messed up.  You've probably worn the tapered surfaces down a bit so the flywheel is bottoming out before it gets snug.

I've had excellent luck with this stuff - Locitite 660 Press Fit Repair.

https://www.henkel-adhesives.com/us/en/product/retaining-compounds/loctite_660.html

Here it is on Amazon:

https://www.amazon.com/Loctite-66040-Quick-Retaining-Compound/dp/B000WTGTAO/ref=sr_1_3?crid=1UUO3LBLWSV2U&dchild=1&keywords=loctite+660+retaining+compound&qid=1630704861&sprefix=Loctite+660%2Caps%2C275&sr=8-3

I had a problem with my BMW rear motorcycle hub years ago.  The steel drive splines ate into the aluminum hub section and it would not stay snug.  Replacement parts were over a thousand dollars, so I thought I'd give the old 660 a try.  It worked!!  25 thousand miles later the hub is good as new.

I would suggest putting in a new key and then gently coating both the crank taper and flywheel bore with 660.  Fill in any gaps or damaged areas between the key and keyway.  (Try not to get too much on so it oozes everywhere...)  Then gently snug the assembly and let it cure overnight.  Once dry, you can torque the nut to spec.

Hope this works!

- Bill

« Last Edit: September 03, 2021, 04:42:23 PM by WConley »
A careful study of failure will yield the ingredients for success.

djburton

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Re: Machinists please step in..way off topic
« Reply #7 on: September 04, 2021, 09:17:17 AM »
Thanks you guys!! Lots of good advice. I'll do the Prussian Blue to see where I stand first and go from there. Last time it was apart,the keyway was not compromised on the crank but will check the flywheel.
  Hey,Bill... so using the Loctite,you just set the flywheel on the shaft with no nut or do you snug it slightly with the nut till dry?
My confidence level just went way up!  Thanks again!

Heo

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Re: Machinists please step in..way off topic
« Reply #8 on: September 04, 2021, 09:21:46 AM »
If the keyway is buggered up, try to peen back the material to where it came from
dont file or grind of the high spots next to the keyway
trying to snug upp the key.  Lapping is the only way to get old Ford V8 Banjo axle
brakedrums to stay in place. Otherwise they shear of the key. The friktion in the cone
is what is meant to take most of the torque.



The defenition of a Gentleman, is a man that can play the accordion.But dont do it

WConley

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Re: Machinists please step in..way off topic
« Reply #9 on: September 04, 2021, 11:38:17 AM »
Thanks you guys!! Lots of good advice. I'll do the Prussian Blue to see where I stand first and go from there. Last time it was apart,the keyway was not compromised on the crank but will check the flywheel.
  Hey,Bill... so using the Loctite,you just set the flywheel on the shaft with no nut or do you snug it slightly with the nut till dry?
My confidence level just went way up!  Thanks again!

djburton - I would gently snug the assembly with the nut.  The Loctite 660 will expand slightly, so you don't want it to lift the flywheel off the taper.  Having the nut in place assures that everything stays aligned and tightens up.  Then you'll be able to really reef it home with full torque.

Let us know how it goes  :D


Edit:  Oh - Be sure to clean off the Prussian Blue (and anything else) with solvent before assembling with Loctite 660.
A careful study of failure will yield the ingredients for success.

WConley

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Re: Machinists please step in..way off topic
« Reply #10 on: September 04, 2021, 11:43:59 AM »
If the keyway is buggered up ...

Heo - I'm glad I could add to your "colorful" English vocabulary  :D   I'm also quite fluent in French swearing, so let me know!

A careful study of failure will yield the ingredients for success.

Heo

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Re: Machinists please step in..way off topic
« Reply #11 on: September 04, 2021, 01:32:25 PM »
If the keyway is buggered up ...

Heo - I'm glad I could add to your "colorful" English vocabulary  :D   I'm also quite fluent in French swearing, so let me know!



 ;D ;D ;D ;D ;D You may not WALK funny anymore but......



The defenition of a Gentleman, is a man that can play the accordion.But dont do it

WConley

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Re: Machinists please step in..way off topic
« Reply #12 on: September 04, 2021, 01:45:25 PM »

 ;D ;D ;D ;D ;D You may not WALK funny anymore but......

"Apporte-moi ta mere, pour que je te refasse!"

That was my grandfather's favorite thing to say to other drivers.
A careful study of failure will yield the ingredients for success.

SMA390

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Re: Machinists please step in..way off topic
« Reply #13 on: September 08, 2021, 08:53:47 AM »
I would definitely recommend the Loctite 660 (green) as we called it. When I would put die sets together for hydraulic stamping presses , we would use the 660 on the guide pins to hold them in the die set. Keep in mind these presses ran at 750 rpm and hit at 125 tons with each stroke. We never had one come loose !  So next time you open a wide mouth beer/soda can or pull the top off a soup can you'll know who made the die sets and machine and why they stayed together.

djburton

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Re: Machinists please step in..way off topic
« Reply #14 on: September 14, 2021, 08:13:32 AM »
Update...Used the Prussian blue and it looks like the flywheel was bottoming out on the skinny end of the taper.I worked it with valve lapping compound and got the fit much better but not perfect.The key and key ways were OK.Applied Loctite 660 like Bill recommended.The nut is a special thin poly lock deal and supposed to be one time use but I rolled the dice and used the old one as it was only used once and it will take 2,3 weeks for a new one.Time will tell but everything is good so far.
  The original problem started when the stater under the flywheel went bad under warranty and the dealer apparently used a hardware store washer under the nut.It was supposed to be a very thick special washer available only from Mercury which I have since replaced.
   Anyway,I consider this fixed and I very much appreciate the help from you guys!  Thanks!

WConley

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Re: Machinists please step in..way off topic
« Reply #15 on: September 14, 2021, 10:22:25 AM »
Sounds like you got it sorted!  Thanks for the update  :)
A careful study of failure will yield the ingredients for success.