Re: Replace Lower Crank Seal on 1957 Johnson 35HP?

They changed to the quad ring about 1959-ish. Reason is, the shaft can move up and down a bit within the bearings. As it does so, the carbon needs to slide on the shaft to maintain contact with the lower bearing. The quad ring is better suited to sliding than an o-ring because the o-ring tends to roll rather than slide.

No need to replace the carbon unless it is broken (or one of the very early ones without the raised sealing surface). Just replace the o-ring / quad ring.