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The gear ring on my flywheel has separated from the flywheel. This gear ring is what the starter engages to start engine. It looks like it slipped off the flywheel, is this correct? Does it just snap back on? I can't see how it was held on to begin with, nothing seems broken. Any advice would be greatly appreciated. Sorry for my description, not a boat mechanic, but would like to avoid having to take it to a shop.
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Starter ring gears, which are not an integral part of a flywheel, are generally held onto the flywheel by an interference fit. The internal diameter of the ring gear is smaller than the outer diameter of the part of the flywheel to which it attaches.
The ring gear is heated, and the flywheel is cooled, so that the ring gear fits over the flywheel. When both parts are joined the starter ring gear shrinks and the flywheel expands causing the two parts to be clamped together.
More than likely you will need a new flywheel.
What is the complete model of your motor? Is it a two stroke or four stroke 25 HP? -
4 stroke F25ELHC
I guess from your description I'm not going to be able to get it back on myself. Nothing appears to be broken, it just slipped off. I can get it part way back on, but as you say it is slightly larger than the ring that came off.Comment
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I have never heard of this happening before.
How did this happen?Comment
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Just going across the lake an hear it make a high pitched noise, slowed down and the noise went away. *****ed for a couple hours with no issue, shut off engine while I put away rods and when I tried to start all you could hear was the starter spin up, because it wasn't engaging the ring gear that had slipped off.Originally posted by 99yam40 View PostComment
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***, hard to believeComment
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Well, if indeed it is a component part of the flywheel then it should be able to be reinstalled. Question is, if it slipped off once will it slip off again.
The flywheel will have to be removed of course to do the work required.
First I have heard of this happening as well. Flywheels coming loose, yes. Starter ring gears coming off, nope.
There is always a first time for everything.
Where is Rodbolt? Wonder if he has seen this.
https://www.youtube.com/watch?v=j_sgiTa3gewComment
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Don't know what say, like I said going across lake when heard a high pitch sound, which I am assuming is when it separated from the flywheel. Slow down and the sound went away, I assume it fell below the flywheel because it ran normal, up until I shut it off and tried to restart.Originally posted by 99yam40 View PostComment
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Sorry for the amateur question, but is replacing the flywheel anything more than taking off the bolt and putting on a new one? Or does how it go back on effect the timing? Again sorry for the non-experience question.Comment
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Seeing is believing.
There are always production tolerances. Maybe your flywheel OD was a bit on the low side and the ring gear OD was a bit on the high side. Who knows why it fell off. But, it did.
Pull the flywheel, lay it upside down and offer up the ring gear to see what the situation is. Mark the ring gear before you remove the flywheel so that you put it back in its original orientation.
Just heat the heck out of the ring gear and see if it slips back over the flywheel. Would not hurt to put the flywheel in the freezer for about 30 minutes either to provide more clearance between the two parts upon reassembly.
Please keep us updated. This stuff interests me. Thanks.Comment
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The flywheel is keyed to the shaft so it will only fit one way.Originally posted by dinohacket View Post
The ring gear should not matter about orientation, except probably like Bossoce said which side was up
You will have to use a puller to get the flywheel off of the shaft
Only way I can think of this ring could come off is the ring gear has a crack in it.
It is a tight fit so the flywheel can ring should be basically the same temperature as the motor heats upLast edited by 99yam40; 08-07-2015, 09:30 AM.Comment
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Thanks for the info, much appreciated. I looked at the ring, spun it around and couldn't see any defect. Just didn't know if new flywheel might be needed. I don't want it to come off again, I was lucky enough to be within a long *****ing motor ride.Originally posted by 99yam40 View PostComment
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You have a 2004 model year motor by the way.
If you don't feel comfortable trying to reinstall the starter ring gear you can probably find a shop who will do it for you for about ten bucks or so.
The flywheel (rotor) is $390 bucks. Yamaha would love to sell you a new one.
2004 F25ELHC Yamaha Outboard GENERATOR Diagram and Parts
In addition to needing a puller, if you replace the flywheel yourself, you will need a socket of the appropriate size and a torque wrench of the appropriate size to reinstall the flywheel nut. Torque for the nut is 116 lb-ft.
Make sure the the flywheel and the crankshaft are clean, dry and free of any debris when you install either a new flywheel or the original one. You might also need a flywheel holder to keep the flywheel from turning when you are torque the nut.Comment
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$390? I think I will give it a go and see how it goes. Thanks again for all the info, this site is fantastic!Originally posted by boscoe99 View PostComment
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I would very closely look at the surfaces where these parts mate. There probably is damage that needs to be carefully cleaned.
I would, if it was mine, probably not be happy just reinstalling the ring without knowing why it came off. (The engine has been going for sometime)
I would be racking my brains to improve on the design (some physical added attachment perhaps).
The cost of any engineering solution (to what must be called a failure of parts) needs to be weighed against the replacement costs of BOTH these parts!Comment
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