Topic: ’58 Big Twin Lower Crank Seal – Antique Outboard Motor Club,Inc

This topic has 22 replies, 8 voices, and was last updated 8 years, 11 months ago by frankr.

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February 10, 2017 at 7:40 pm #6317
Mumbles
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This is the order the lower seal was installed in a Big Twin I’m working on. First, the bearing, then the two piece, as in ‘broken’ carbon seal, then the quad seal which was sandwiched between the carbon seal and the large cup washer on the spring. Something don’t look right here. Shouldn’t the quad seal have been inside the carbon seals slot where an O ring normally goes?

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February 10, 2017 at 10:07 pm #52778
chris-p
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Yup!

Which way was the carbon seal installed? I find they seem to be cracked when installed upside down.
February 10, 2017 at 11:03 pm #52786
Mumbles
Participant
Thanks Chris, I kind of figured that.

One chunk of carbon has a worn area on it. I’ll take a look when I go out and try to figure which way it was installed.
February 11, 2017 at 12:31 am #52799
garry-in-michigan
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Lifetime Member
I have seen a lot of them break by trying to slide them in place without oiling the quad ring. Of course the rim of the metal cup that pushes against the carbon seal keeps the spring centered. . . 😉
February 11, 2017 at 2:39 am #52807
Mumbles
Participant
I’m pretty sure the carbon seal was installed the proper way except the quad seal was placed between it and the springs cup washer. The carbon halves were kind of cockeyed when I split the cases so the one half must have been rubbing on the lower bearing. You can see the wear pattern in the one half. This might explain why the bottom piston was scuffed a bit to. The lower cylinder was probably running lean or else water made its way in to wash the fuel mix off the piston.

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February 11, 2017 at 12:29 pm #52816
fleetwin
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US Member
I’m not afraid to admit, I still don’t fully understand how this carbon seal system works! But yes, the quad seal should have been inside the carbon seal groove….
Another question. Did this system always use a quad seal type oring? Or, was the original style oring updated over the years…
February 11, 2017 at 4:16 pm #52830
garry-in-michigan
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Lifetime Member
The quad ring seals the carbon seal to the crankshaft, and spring pressure leaves a film of oil between the carbon and the bearing. Ware resistant and waterproof. What more could you want? . . . 😀
February 11, 2017 at 7:49 pm #52836
chris-p
Participant
Fleetwin, Yes always used a quad ring. I have never found any evidence against that anyways? Has anyone else?

Something else to note. The carbon seal itself was updated at some point, I forget what year off hand. The 302538 seal had a narrow face machined on the lower side of the seal which abutted the bearing. The original seals are straight and flat. This narrow face provides a better seal, and prevents oil from accumulating on the mag plate, for the top seal.

If you take a motor apart, and find the flat carbon seal, you should update it to the one with the machined face.
February 11, 2017 at 10:29 pm #52843
William Jatzek
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What year big twins used a quad ring seal ? Did some use O rings ? What is the part number for the quad ring seal? Bill,
February 11, 2017 at 11:36 pm #52847
Mumbles
Participant
I’m pretty sure ’58 was the first year for the 305098 quad seal while the previous years used the 302540 O ring.
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