My Flywheel Is Rubbing

[stephenspann27]

1965 18hp. I bought this motor not running, I replaced one of the coils (the black one). The coil is only rubbing one side of the flywheel, the outside edge of the coil is rubbing, and the top of the coil is rubbing. What is strange is that only one side of the flywheel is touching, does this mean the crank is bent, or is the flywheel casting imperfect?

 

[GA_Boater]

stephenspann27

Fixed your hijack in an old thread.

 

[Vic.S]

Check/ readjust the positioning of the coils on the base plate

See the item [FONT=&quot]"How to Change Coils and set points on old OMC's"[/FONT]

on the Engine FAQs board http://forums.iboats.com/forum/engi...w-to-change-coils-and-set-points-on-old-omc-s

There should be no need to change either if they are good

 

[F_R]

The short story is that the coils are NOT supposed to be touching the flywheel magnets. Either the armature plate is worn and wobbling, or the shaft is moving back and forth (worn bearings), or most likely the coil position merely needs adjusting. Move them back till flush with the machined edges on the armature plate, or just a hair more. Too far back will affect spark strength.

I notice your flywheel keyway is battered, caused by improper installation. Shaft and flywheel tapers must be clean and dry and you must use a torque wrench to tighten nut to 40-45 foot pounds. Failure to do so can result in catastrophic damage.

 

[stephenspann27]

If the crank bearings were wobbling you'd think it would be rubbing both sides of the flywheel... I went ahead and ordered another green style coil, like the one that isn't rubbing. I'm going to give that a try first. The key did sheer on me the first time i reinstalled the flywheel, I got the torque specs later, and I've been torquing it correctly. If the new coil doesn't do the job, I'll install the flywheel and run the dial indicator on the flywheel and see if I get some walking there. Maybe a new flywheel is in order, or possibly crank bearings.. or armature plate.

 

[Vic.S]

If the crank bearings were wobbling you'd think it would be rubbing both sides of the flywheel... I went ahead and ordered another green style coil, like the one that isn't rubbing. I'm going to give that a try first. The key did sheer on me the first time i reinstalled the flywheel, I got the torque specs later, and I've been torquing it correctly. If the new coil doesn't do the job, I'll install the flywheel and run the dial indicator on the flywheel and see if I get some walking there. Maybe a new flywheel is in order, or possibly crank bearings.. or armature plate.

Have you tried checking and repositioning the coil that is rubbing.. That may be all that is required ?

 

[stephenspann27]

Have you tried checking and repositioning the coil that is rubbing.. That may be all that is required ?

Yes sir I did. I positioned it as far toward the crank as possible. It still rubs, it's not just rubbing on the outside, the top of the coil is rubbing the underside of the flywheel is well. The body of the black coil looks to be bigger than the body of the green coil. In the other thread where I posted originally, someone said the sierra castings were sometimes oversized.

 

[gm280]

I don't think you have any defective parts. I think you have the coil installed too far out from the center. Like previous said, the coils have machined posts that the coils are suppose to be aligned with. Even a few thousandths forward of those machined areas and the flywheel will hit. So simple reposition the coil that is hitting the flywheel back just a little and happy boating. New parts are not going to fit this because it isn't a bad part. You will only have a spare laying around. I also suggest you clean up the tapered shaft and flywheel sections to good clean dry surfaces. Then install the flywheel and a good key and torque to the proper torque and I think everything will work well. JMHO

 

[F_R]

Yes sir I did. I positioned it as far toward the crank as possible. It still rubs, it's not just rubbing on the outside, the top of the coil is rubbing the underside of the flywheel is well. The body of the black coil looks to be bigger than the body of the green coil. In the other thread where I posted originally, someone said the sierra castings were sometimes oversized.

Well, that presents a different problem. If the top of the coil is rubbing the underside of the flywheel, that would seem to indicate the flywheel is too low (??). That could be because the crankshaft is moving up and down too much, or the flywheel taper is spread from somebody in a prior life overtightening the nut (like with an impact wrench). OR, of course the coil could be oversize. It's kind of hard for us to diagnose it from a distance.

BTW, I assume you have figured out that only the magnets pass close by the coils. The bump on the opposite side is only for balancing purposes.

There have been reports of some aftermarket coils not fitting properly, no matter what you do. I hope you don't have one of those.

 

[gm280]

How bad is the top of the coil hitting the flywheel? I ask because if it is mere striking a little, you could sand down a little for that to work. Then see if the coil itself is hitting the magnet area yet. I think you stated that you ordered another coil. If so see how that fits. If it hits also, you have other issues. But if that one fits without any issues, you may contact the other coil's manufacturer for a new one. JMHO

 

[stephenspann27]

New coil will be here tomorrow. I'm not going to sweat it, until replace it with one of the green coils which has a smaller body.

 

[stephenspann27]

I have installed the new coil, the body is in fact smaller and it doesn't appear to be rubbing. Still though, when I rotate the flywheel I see the mag plate shake a little bit. I think the problem is where the timing arm mates to the throttle gear, I think there is too much slop there. I've included some pics and a video. I can rock the mag plate if the throttle is anywhere in between "stop" and "fast"

Video:

https://www.dropbox.com/s/a5ml6ut1ne...58.55.mov?dl=0




https://www.dropbox.com/sc/nelayqrcn52781z/AADSpgGwjFjCeRVeokd6dQ4Ua

 

[stephenspann27]

Looking at the parts diagram, I am missing this pin

 

[stephenspann27]

 

[stephenspann27]

Got some wear in the linkage, video: https://www.dropbox.com/s/6t88z7kb6pxzsaq/2016-10-20 17.59.51.mov?dl=0


Turns out that pin isn't missing, it's just broken. I ran a bolt through it for now.