Substitute for OMC Shift O-ring #301877, Sierra 18-7100

[Sputter]

If I drive 183 miles from Portland to Seattle, I could buy these o-rings for $0.40 each at Fisheries Supply on North Lake Way. The prices I see online can be $10-$30 when you include shipping –for an O-Ring!

I’ve looked at standard o-ring charts and can’t find anything close.
The dimensions are listed as ID = 0.245″, cross section = 0.155″

Has anyone found a substitute?

Some websites show this o-ring crosses with Mercury Quicksilver O-RING 25-85594. Can anyone confirm fitment?
The 25-85594 pack of 4 is available on eBay for $8 with free shipping.

1956 Johnson 15 Hp, FD-10
1958 Johnson 5.5 Hp, CD-15

[frankr]

Sierra Marine sells a substitute, but I have found them to be a bit on the incorrect size.

Yeah, you aren’t paying for the part, but mostly the shipping and handling. Somebody has to be paid for doing the paperwork, stocking and, pulling the parts, packing, postage, ect.  Just a sign of the times.

BTW 301877 was 10 cents in the 1964 Parts Price Book..

[Sputter]

I know how that goes! LOL

I had a handyman business and doing the billing, accounting, stocking supplies, and gathering the tools for a particular job took lots of time that I didn’t get paid for.

I’m just hoping that there’s a common automotive or industrial substitute that I can get locally. The need for sealing 1/4″ shafts must be fairly common. The OD is about 0.4″

1956 Johnson 15 Hp, FD-10
1958 Johnson 5.5 Hp, CD-15

[joecb]

Just a hint on custom fitting “O” rings. If you can find a ring that is close but maybe a bit too fat, try reducing the OD. Mount the ring on a spindle or machine screw between a couple small washers and spin it in your drill, fine sand paper will reduce the OD, Trial and error until you get the fit right.

Joe B

1 user thanked author for this post.

Sputter

[billy-j]

frankr wrote:

Sierra Marine sells a substitute, but I have found them to be a bit on the incorrect size.

Yeah, you aren’t paying for the part, but mostly the shipping and handling. Somebody has to be paid for doing the paperwork, stocking and, pulling the parts, packing, postage, ect.  Just a sign of the times.

BTW 301877 was 10 cents in the 1964 Parts Price Book..

Hello. What “O” ring would you buy as a replacement? A new “O” ring from Bombardier? What are your thoughts regarding this part going in to the future. I have several projects that would need this part.

[billy-j]

frankr wrote:

Sierra Marine sells a substitute, but I have found them to be a bit on the incorrect size.

Yeah, you aren’t paying for the part, but mostly the shipping and handling. Somebody has to be paid for doing the paperwork, stocking and, pulling the parts, packing, postage, ect.  Just a sign of the times.

BTW 301877 was 10 cents in the 1964 Parts Price Book..

Hello. What “O” ring would you buy as a replacement? A new “O” ring from Bombardier? What are your thoughts regarding this part going in to the future. I have several projects that would need this part.

[Sputter]

I’m going to try some of the Mercury O-RING 25-85594 and see how well they fit. They’re OEM for Mercury and the Sierra 18-7100 is supposed to cross. The size is given as 0.239″ x 0.174″. That would make it a little snug on the shift shaft, and 0.578″ OD vs 0.555 OD on the OMC o-ring. That’s an OD difference of 0.023″. Interestingly, the ones I ordered are orange.

I like to experiment. Who knows, the Mercury might make a better seal.

1956 Johnson 15 Hp, FD-10
1958 Johnson 5.5 Hp, CD-15

[billy-j]

Sputter wrote:

I’m going to try some of the Mercury O-RING 25-85594 and see how well they fit. They’re OEM for Mercury and the Sierra 18-7100 is supposed to cross. The size is given as 0.239″ x 0.174″. That would make it a little snug on the shift shaft, and 0.578″ OD vs 0.555 OD on the OMC o-ring. That’s an OD difference of 0.023″. Interestingly, the ones I ordered are orange.

I like to experiment. Who knows, the Mercury might make a better seal.

Mabbe the orange is that viton rubber that is alcohol resistant. Let us know how they work.

[Sputter]

Here are some pics of the Mercury Marine o-ring with my casing and shift rod.

The pic with the package shows my original, dried up o-ring beside the new orange one. The orange ones I think are new old stock.

The orange is a coating that flakes off with handling. I’m guessing it’s not supposed to do that, but the o-ring is plump and soft.

When I dry fit the o-ring with the shift rod, it was snug to the point where the o-ring would pucker in and out when I slid the rod. It seemed workable as is, but I decided to squirt some motor oil in the well to see if it improved the function or leaked.

I’m happy to report that the oil made the shift rod slide effortlessly, and the o-ring was like a squeegee, only allowing a light oil film pass by. The oil remained pooled on top of the o-ring.

I’m calling it a successful substitute for the OEM Johnson o-ring.  If the o-ring fails the pressure test, I’ll post a retraction! Lol

 

1956 Johnson 15 Hp, FD-10
1958 Johnson 5.5 Hp, CD-15

[WillinMKE]

Thanks for following up, Sputter.  Would you please post the pressure test result, pass or fail?  Good info for folks to have when searching for this in the future.

I found an old post from Ben / ‘fisherman6’ here on this site / ‘OldJohnnyRude’ on YouTube.  He said he uses:

“Metric O-rings 6mm ID x 4.5mm CS in 70A durometer Buna N. I buy my O-rings from theoringstore.com.”  … “They are a little tight, but work well if you make sure there are no sharp edges on the shift rod and use plenty of lubricant when you push the shift rod thru. Once they are together, they seal up nicely.”

Post here: https://www.aomci.org/forums/topic/omc-shift-rod-o-ring-301877/#post-79482

Using that info, I found what I think is the one he references here:  https://www.theoringstore.com/store/index.php?main_page=product_info&cPath=368_12_482&products_id=17404

Min qty. 40 at a whopping 10¢ a pop, so if that’s correct that’s way cheaper.  Can anyone verify that the oringstore.com part # N4.50X006 linked above is correct?

-Will

[Author]

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