18 hp magneto cam

[Sugashane]

I think my flywheel may be shot, but i wanted to run it by you guys before i went and bought a new one. Everytime i try to tighten down the flywheel, my magneto cam snaps. The cam shaft looks to be in perfect shape. Is it because the flywheel is wollered out and pushes down on the cam? is it time for a new one?

 

[tashasdaddy]

Re: 18 hp magneto cam

what 18 there are a lot of them. don't really follow your question. picture would help.

 

[Sugashane]

Re: 18 hp magneto cam

it's a 1961 model. I don't have a picture, but the magneto cam/points cam is directly under the flywheel on the cam shaft. for some reason, everytime i put on a new one, and try to tighten the flywheel, it cracks the cam. i was told that the flywheel was supposed to tighten down onto the shaft and not the cam. but it is apparently pushing on the cam itself before it tighten to the shaft. I assume that the flywheel is bad. just wanted to make sure.

 

[Sugashane]

Re: 18 hp magneto cam

bump

 

[Rick.]

Re: 18 hp magneto cam

Something isn't going right here. I have heard of flywheel replacements before but not because the hole is the wrong size. The points cam has "top" stamped on it are you getting it on right? Is your key way in place? Are you lining up the flywheel slot and the key way? A little history might help here. Have you seen this motor running in the past? Best of luck. Rick.

 

[tashasdaddy]

Re: 18 hp magneto cam

read this, something is wrong. http://forums.iboats.com/showthread.php?t=294072

 

[tx1961whaler]

Re: 18 hp magneto cam

It is possible that the flywheel is shot. If it were repeatedly overtightened, wrong type of puller used, etc, the hole could be spread. This would let it get drawn down too far and contact the cam. I'd rule everything else out first, before I got a new flywheel.

 

[F_R]

Re: 18 hp magneto cam

It is possible that the flywheel is shot. If it were repeatedly overtightened, wrong type of puller used, etc, the hole could be spread. This would let it get drawn down too far and contact the cam. I'd rule everything else out first, before I got a new flywheel.

100% agree. Somebody has overtightened that flywheel and spread the hub. Happens all the time when somebody uses an impact wrench to tighten the nut. That's one reason I keep harping about using a torque wrench to tighten it to the proper specs.

You need a flywheel.

EDIT: Putting oil on the tapers will cause a spread hub also. They must be clean and dry. You still need a flywheel.

 

[Rick.]

Re: 18 hp magneto cam

That's very interesting. I would have thought it would be impossible to open the hole that much. Thankfully I have and use a torque wrench.

 

[tx1961whaler]

Re: 18 hp magneto cam

The flywheel is actually soft metal. I've been told (could be bs) that is to prevent cracking and crack propagation, which would eventually cause a heavy piece of metal rotating at 4500 rpm to go slinging about. That would be bad.

 

[Rick.]

Re: 18 hp magneto cam

Ya. We would have to armor plated cowlings!!! More weight and wasted HP too. Sounds reasonable to me but you think of some of the drive pulleys that are around and I don't see them ripping apart. I always though F_R was telling everyone to torque to prevent the key way breaking. I never really understood you could damage the flywheel by getting them too tight. Every day I lean something from someone at Iboats.com. And I'm grateful. Rick.

 

[Woodstock60]

Re: 18 hp magneto cam

I had to strip a few important bolts to learn the torque wrench lesson.