TOPIC: outboard flywheel balancing

using a flywheel from ebay and a starter ring gear from another engine, do these need to be balanced together before installing? how is that done?

In my experience you should have no issues with this. Not like flywheels, harmonic balancers, and crankshafts in automotive engines, where some parts may have been balanced with others. Bolt 'em up and have at it. I'd use some Loctite Blue on the starter ring bolts.

Be sure the crankshaft taper is clean, key in good shape, and the inner bore and keyway of the flywheel is undamaged.

If there are any irregularities in crankshaft or flywheel tapers, use some fine valve grinding compound and lap the flywheel in (without the flywheel key in place) to the crankshaft. Be sure to clean all that gritty stuff out before assembly!

Torque the flywheel nut to factory values.

HTH & G'luck with the repairs.........ed

Thanks for the insights Ed. The referred to manual is THE evinrude repair manual. I'm swapping a 63 power head from a parts engine onto a 66 engine after the last flywheel install wet bad and melted the crankshaft/flywheel. I previously had it apart a few times to do tune-ups but something went wrong with the last install. I'm concerned about a little wobble between the tapers without the key, the flywheel sits down to the bottom of the taper and there is a little wobble between the two... I'll try the lapping procedure...

That doesn't seem right. The flywheel should not be bottoming out at the bottom part of the crank, the taper of the flywheel is supposed to set right down on the crankshaft taper. There should be absolutely no movement, rocking, or whatever of the flywheel when it's sitting on the crankshaft, without the key in place.

BTW, when the flywheel is down far as it'll go, does any portion of the untreaded part of the crankshaft protrude beyond the surface of the flywheel?

It should never get that close. In other words, with the flywheel nut fully torqued, the end threads should be the only part of the crankshaft sticking up above the surface of the flywheel.

Otherwise, the flywheel nut would bottom out on the end of the crankshaft and could not be doing its job of holding the flywheel to the crank.

That is what I thought too, therefore the inquiry. there are only threads protruding above the top of the flywheel. Maybe the lapping will true the tapers....

Sounds like a good plan! Keep in mind that getting the flywheel nut torqued to specs is critical on these Big Twins. If you don't, it'll shear the key.

Your 40hp should have an approx 1-1/16" flywheel nut, and the torque on that nut should be 100-105 ft-lb.

Note that earlier 40's had a smaller crankshaft nut (around 7/8" IIRC) and this was torqued to 65 ft-lb.

ok good to know those torques. Also, lapping didnt help. It seems like the flywheel is bottoming out before the tapers engage. I ground off some of the bottom and enlarged the champfer, still not seating. I'll get some bluing to show where the interference is...

You've got the wrong flywheel. What it's doing should never happen. I've never had the correct flywheel not fit properly on a crankshaft. NEVER in over 50 years of working on outboards.

Now, it may be your '63 has the older-style crankshaft for some reason or another, and needs a flywheel with a smaller taper.

Again I ask, what size is your flywheel nut? Measure across the flats and let us know.

This is the nut that fits the crankshaft currently installed in your powerhead. Only then are we gonna know the true solution to your issue.

I dont have the original nut, it's a parts engine. are the treads the same between the different sized cranks? the nut i have is from the '66 (I think) and does thread onto the '63 that I want to use. It measures 15/16. Now, the flywheel that went bad on the 66 was from the parts engine that I am now trying to use. According to marineengine, the same cranks were used on both engines. Would the tapers change without changing the part numbers? The ebay flywheel p/n is 580408 the same as the p/n on the original the '63, (and the same as the original '66). Marineengine calls for a 580410 flywheel for the '63... I really appreciate your expertise and time to work with me on this. Im not trying to challenge you just saying what I have here...Thanks for your help

Well, I don't know what to think about the different part numbers! You can find both the "408" and "410" flywheels on eBay and they look identical. They are definitely the larger taper model, and have 24 ribs on the bottom side of the flywheel.

The older flywheel P/N is 580334 and this flywheel was used by '61 and earlier. '61 and earlier also use a different flywheel nut (I'm assuming the smaller nut). This flywheel has 7 ribs cast into the bottom and also has a removable "window" on top, that gives you access to the points adjustment.

OK, well I had to do enough nosing around to prod my pore ol' tired brain cells into action; Nice thing is, you can look up part numbers on Marineengine.com, then go search on eBay. Something as common as this engine, you're guaranteed to find the parts listed, and usually decent pictures.

So what I dredged up was some good pics of an early 40hp crankshaft ('61 and earlier), P/N 307482, and the '62-up crankshaft, P/N 311356. Which jogged my memory further, as to the difference between these 2 crankshafts. And it's unmistakable!

The earlier crankshaft, besides having a smaller taper and smaller diameter, has a hole bored in its side, and the pin for the points cam goes in this hole. The points cam slides down the crankshaft O.D. and comes to rest on the shoulder of the crankshaft, with the pin keeping the cam in proper time.

The later crankshaft has a larger taper and larger threads on the end. Plus the points cam is integrally cast and machined as part of the crankshaft. It doesn't come off, in other words! So there's no way to get these 2 styles of crankshaft confused with each other.

See the attached pics and the difference is obvious.

So if you have a separate points cam, it's an older powerhead and you need a smaller-taper flywheel.

If you have an integral points cam, then you need the larger-taper flywheel and I might suggest that there may be a problem with the eBay flywheel, considering that the part number should be compatible with a large-taper crankshaft.

The Million-Dollar Question is, Which One Do You Have?????????

Hope that Helps Finally!!...............ed

The cam is machined into the crankshaft. It was listed as 580901, which is a flywheel/ring gear assembly using the 580408. The numbers are hand written on the original OMC box. hand written 580410 is crossed off with 580901 written on the side. Who knows what it is. I'll get some bluing to see the interference. It just teeters a little bit with a little tick sound, even after hitting it down with my hand...

The bluing showed interference on the chamfer, so I ground a little bit whit the Dremel and the teetering is gone! there was some scoring on the crank taper from the fine laping compound so used some 400 then 800 sandpaper to polish it further. Still a little scoring but much better. Thanks again for your kind advice and research!

By the way, the engine is going on a '58 Shell Lake 16ft Rocket, which I just noticed is featured on the left side of the Fiberglassics web page header. the image is from the cover of the sales brochure...

Sounds like good progress. The more contact you get, the better. When you get a good bluing pattern you'll know you're there! Glad it worked out without a bunch of Strange Stuff going on. Just the typical things that happen!

There is a slight rotational slip before the flywheel grabs the crankshaft and they turn together. Is that a concern? More lapping?

A touch more grinding on the flywheel chamfer as indicated by bluing seems to have fixed it.