Scott-Atwater 30HP lower unit seals

[jpatti75]

Before I pull out my calipers and make a ham-handed effort at measuring seals, has anyone had any luck matching Scott-Atwater lower unit seals to current seals by SKF? I am working on a 1956 Firestone 30HP, which has the same lower unit as the 1955 Scott-Atwater badged 30HP and the 1956 S/A 33HP. NAPA/Sierra used to make a lower unit seal kit (18-4810), but I haven’t been able to track one down. The two oil seals on the lower unit that I need most are:

Prop Shaft Seal – original part 3654-3109
Drive Shaft Seal – original part 3654-3186

Every other seal in the lower unit is an o-ring, so I am less concerned about tracking those down. I know this is a long shot, but I appreciate any info anyone has on these tough-to-find parts.

Thanks,
JP

[retiredoz]

Hi Jason, Best I can do is the Sierra nos for your seals are 18-2127 for the driveshaft seal, and 18-2132 for the prop shaft. I don’t have anything that crosses to seal makers…And these are OLD numbers, I found one of them is already reassigned to as trim hose..

• This reply was modified 5 years, 2 months ago by retiredoz.

[jpatti75]

Ozzie,

Thanks so much … that is a big help!

It looks like Scott-Atwater may have been using Chicago Rawhide (CR) as their supplier, as upon close inspection of the seals, they both had CR numbers stamped into them. I typed the numbers in SKF‘s online CR interchange tool (https://www.skfextranet.com/crsealsfinder/ ) and was able to find current SKF part numbers, which I also cross referenced to Timken. Here were my results:

Drive Shaft Seal
SKF 6903 (original CR 11120)
Timken interchange = 450009

Prop Shaft
SKF 10049 (original CR 1831)
Timken interchange =450593

With those and your Sierra numbers, I now have some options to go shopping! It’s nice that there is some hope for guys looking for Scott-Atwater seals if they were using CR seals.

Thanks, again, for your help. Always good to hear from you, too. (This is my first post in a long time.)
Jason

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