Shaft ball bearings for 1979 Yamaha 3.5 AC 642 two stroke outboard.

[Brian Anderson]

I bought a 1979 Yamaha 3.5 AC 642 two stroke outboard last summer. Good motor, ran great for more than 100 hours. Now I have a problem with the crankshaft ball bearings and need to replace the top one, at least, though both would be better. The Yamaha part number is 93306-00407. The manufacturer's part number on the ball bearing is NTN EC-6004/46C3. The odd thing about this part is that apparently the 6004 bearings today at least have the dimensions 42 mm outside diameter, 20mm inside, 12 mm wide. But this bearing is 46 mm x 20 mm x 12 mm, which apparently doesn't exist in a standard ball bearing.

It occurs to me that Yamaha probably didn't use this custom ball bearing just for this outboard. But Yamaha long ago stopped supporting this motor and the manufacturer's part number no longer works and neither can I search for the simple size for bearings. Is this bearing still available through Yamaha under another part number? Or failing that, is there another part number for a newer model that I might be able to find on the secondary market elsewhere?


I really like the motor, and I'd really like to keep it going, but this bearing is going to die soon, and kill the motor with it, I think.

[panasonic]

When I Google the NTN part number

https://www.noc.ua/en/online-catalog...EC-6004%2F46C3

[Brian Anderson]

Panasonic - Yes - that's a shop in the Ukraine - I contacted them about the bearing, they said they do not have it, but hoped if I needed a different ball bearing in the future, I would order it from them. So it sounds like they don't expect to get it any more. That's the only place on Earth I could even find mention of the part. The odd thing about it is that basically the number 6004 means a deep groove 42x20x12 ball bearing. The C3 at the end means extra clearance, the /46 is unusual as far as I could read because after the / the letters and numbers are normally talking about what kind of seals are installed, if any and things like clearance. But here it means the outside diameter is 46 mm instead of the standard 42.

So I was hoping a Yamaha tech might be able to say OK well that bearing was also used in 10 other models of Yamaha motors, and here are the part numbers you can look for. There are a lot of new/old Yamaha parts for sale various places. But like I said, the Yamaha parts numbers are a black box for bearings. There's no info on the type and dimensions of the bearings.

[99yam40]

I would not think Yamaha would have multiply different part numbers for the same bearing.
would someone be able to make a sleeve for a regular bearing to make it fit?

I wonder how thick speedy sleeves are

[Brian Anderson]

99yam40 A couple of people have suggested a sleeve if I can't find the part. But this is the first time I've ever been so deep in a motor, and I have no background in it. Where might I pose the question to somebody at Yamaha who might know about bearings?

The motor is otherwise really pretty clean considering its age. Except for the parts problem, no reason it shouldn't keep running for quite a while.

[panasonic]

if you can’t find a bearing..then have machine shop make you a sleeve. I don’t see any other option.

[Bluefish]

Here's a link to MSC for your bearing. https://www.mscdirect.com/browse/tn/...chterm=bearing

[Brian Anderson]

Bluefish, thank you but unless I'm missing something, those bearings are all the standard 42 mm outside dimension. The whole issue is that the bearings I need are 46 mm outside dimension, not 42. Yamaha apparently had a custom size made for this motor that is today impossible to find.

[Bluefish]

Sorry looked at the wrong numbers. You could get the 47 mm bearing and go to a machine shop and have them take the 1mm off the bearing its not a big cut, the 2mm of height should not be a problem? don't know how much play you have in the head housing a little sanding would give you a nice press fit? it is a 40 yr old motor your trying to keep running some will say its a crazy idea, i fell 1mm is not a lot if there is wear in the housing

[Bluefish]

Sorry looked at the wrong numbers. You could get the 47 mm bearing and go to a machine shop and have them take the 1mm off the bearing its not a big cut, the 2mm of height should not be a problem? don't know how much play you have in the head housing a little sanding would give you a nice press fit? it is a 40 yr old motor your trying to keep running some will say its a crazy idea, i fell 1mm is not a lot if there is wear in the housing https://www.mscdirect.com/browse/tn/...chterm=bearing

[99yam40]

now taking out .5 from the case(total 1 mm) does not sound like a bad idea.
I am sure a machine shop could do that

[Bluefish]

If your trying to save money maybe a brake cylinder hone will do just cut the stones shorter for proper pressure. Or you can go the other way and get the smaller bearing and use shim stock around the outside. Or get a long blade Feeler Gage Set for and assortment of sizes.
And add this to if you feel the need https://www.mscdirect.com/product/details/90064676

[Brian Anderson]

That's an interesting idea - a friend on another forum suggested the same thing. I'm obviously no machinist or I wouldn't be asking these questions. In fact the width of the bearing is pretty critical - it butts against a lip in the top of the case, and then there's a steel retaining ring on the bottom before the seal and it's tight, no slack in there at all. Ideally I guess I'd have two cut, 1 mm from the width each side and 1 mm from the outside diameter. Alternatively there is a 45x20x12 bearing made, and people have suggested it would be possible to pop a sleeve on that, or even on the 42, and then turn it down to 46 mm. I don't really have a good feel for what would be better -- seems to me the sleeve, even on the 42 mm bearing would be simpler. But I don't know.

[99yam40]

I agree, do a search for speedy sleeve and call to see what is available

[Bluefish]

Yes, then go with the smaller bearing, there’s no problem with height and ID and if you can find a speedy sleeve for the OD great. If not shim stock or feeler gauge and trim blades as needed for the OD.