'67 40 Rude flywheel key

[68whaler]

I ordered a new key for my '67 40 hp selectric flywheel. Dealer got me #307480 but it looks too small - might disappear into flywheel slot. It is only about 9/16" long and 3/16" deep. Has the ridges on the side so once forced into crank it is stuck there. Can this be the right one or do I need somewhat larger? Former flywheel was so eaten up that someone had installed one that was obviously too large. Help Paul

 

[Paul Moir]

Re: '67 40 Rude flywheel key

That ought to be the correct key. I measured one here, about 5/8" long, 3/16" deep, about 5/32" wide. The key does not have protrude much (1/16") from the crank, but it must fit the slot in the flywheel closely so there can be no movement of the flywheel on the crank before the nut is tightened.<br /><br />Is it possible you have some other flywheel? The '60 and earlier ones were different, as well as some of the later ones.

 

[68whaler]

Re: '67 40 Rude flywheel key

Am sure the flywheel is correct Paul. Is an exact match for the original but that one was eaten up by too many winter's worth of mouse nests. Is amazing how corrosive mouse urine is. I guess all is well, will touch up points and clean it all out well before reinstalling. The refurb on the 68 whaler is coming along beautifully as well, thanks again.

 

[Joe Reeves]

Re: '67 40 Rude flywheel key

The key must be aligned so that the outer edge is vertical with the engine, not aligned with the crankshaft taper.<br /><br />The flywheel nut must be torqued to 105 foot pounds. Any less will result in a sheared flywheel key and damaged tapers of the crankshaft and flywheel.

 

[68whaler]

Re: '67 40 Rude flywheel key

Thanks Joe, would be lost without you guys who are experts in here. You would be impressed with the puller I made to get the flywheel off.

 

[R.Johnson]

Re: '67 40 Rude flywheel key

The damage, or corrosion you are looking at is more than likely caused by the flywheel running loose. Does the corrosion look like fine red powder with pit's on the crank, and flywheel hub? In machine work, this is called spalling. It is caused by rapid vibration between two mating part's. Can you clean up the part's by lapping? The close fitting taper with proper torgue is what hold's these part's together. The key is for alignment.

 

[68whaler]

Re: '67 40 Rude flywheel key

The corrosion on the old flywheel is in fact due to mouse **** - looks like an old saltwater engine. There are however, two areas of pitting on the crank, lapping sounds like a great idea - silicon carbide?

 

[68whaler]

Re: '67 40 Rude flywheel key

Oops! What grit size? I could get diamond grease from the guys over in the metal trades side of the house.

 

[R.Johnson]

Re: '67 40 Rude flywheel key

Depending on the amount of damage, I would start with a medium grit. If you can get some, that diamond grit should be great. It will cut guickly, and leave a nice finish. When lapping, don't try to remove all of the pit's. Go just enough to leave a good surface on both contact's. Keep in mind when dealing with taper's, removing a small amount of metal will make the flywheel ride deeper on the crankshaft with very little metal removel. Don't go so deep that the flywheel may strike the ignition coils'. Remove all trace's of grit when finished. Let us know how it works.

 

[Paul Moir]

Re: '67 40 Rude flywheel key

I find that's a good thing to do even when you're just changing one flywheel for another. Occasionally there's a very slight difference.

 

[68whaler]

Re: '67 40 Rude flywheel key

Thanks Paul and R. Johnson. I get mixed opinions from the guys in the machine shop but think I will give it a try as I am certain the previous keyway was oversized and recognise how critical the fit is.