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flywheel and shaft problem: 96 Mercury 50hp 2stroke

J

joachim

New member
Hello guys,
I have a problem with the Flywheel and crankshaft of my 96 50hp Mercury 2 stroke 3 cylinder. There were issues with the stator and switchbox and while testing what was wrong the key in the shaft broke several times. Until that problem was recognized, the shaft and flywheel (the part where it sits on the shaft) were worn out and the flywheel had some play, which again led to the key braking all the time.
I bought a new flywheel but it seems like it still has some play. This would indicate that the shaft is worn out too much as well. :confused:
I have some pictures of the shaft here:

https://www.dropbox.com/s/bt7vmzv63ysr7sv/20140426_163147.jpg
https://www.dropbox.com/s/ar8gft8wiiscbml/20140426_163157.jpg

My question now is if if there is anything to do, to fix the flywheel to the shaft, like with some special glue or fill the small gap (it can only be like half a millimeter or so) with some kind of metal.
Or would I have to change the shaft in any case?? And if yes, how much working hours would a mechanic need for that?? Would that be economical after all for such an old engine??

Thanks a lot in advance for your help,

Jo
 
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Hmmm, there is a couple of shop owners here that could probably give you a better quote, but I can give a bit of a guess for you.

IF (IF) the crank needs to be replaced you could be looking at a couple of grand quite easily.

The whole block would need be torn down. The cost of the crank itself is 700'ish bucks, and of course you will re-do the seals and probably the crank bearings while you are at it.

Then, since the connecting rods need to be removed as well - at least the lower end, other issues may become apparent. That could lead to (almost) a rebuild plus the new crank - a potential can of worms.

Albeit, still significantly cheaper than a replacement motor.

If I were you I would contact a local machine shop and get an opinion from them. They can sometimes do "some magic". They may be able to rework something for you (like put a bushing in the flywheel ????? that would tighten up the hole) - at least worth asking.
 
You just needed to buy a small tub of valve grinding compound. Could have lapped the flywheel and crankshaft together.--This would remove imperfections on the 2 tapers.--------The key locates the flywheel for proper timing , but the locking tapers drive the flywheel.
 
Right! Hydro racers do this all the time, and it works fine. Done a few myself with complete success.

Be sure to remove al traces of grinding compound when you are done, and do NOT use any lubrication when installing the flywheel. Friction--not the key (only for location) is what keeps the thing from moving

Jeff

PS: . I've run motors without the flywheel nut after it while I was starting them with a drill! eedless to say, I careful shut them right off.
 
Hi guys - thanks a lot for your responses! Will give the grinding compound a try then!! I have two flywheels to try this with - one virgin one and the one where the taper is damaged. I am bist scared to try with the new one, what would you do?? And do I get this right:
get the flywheel key out
put some grinding compound on the shaft
put the flywheel on and turn it left and right until it fits
remove the grinding compound and clean parts nicely
put the flywheel key back in and install the flywheel??
Thanks again in advance, best, J
 
The key may be special so do not just get one from a bin in a harware store.---Order a factory one.-------This procedure is very common and recommended in service manuals too.
 
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