what does this rubber washer do?

[opposedtwin]

part number 203355. in the diagram it is #72. this is a part in the carb of the FD-10, 11 and 12 models by Johnson. I got one and can’t figure out where it installs, or what it does. the only place it fits is on the barrel of the low speed packing nut, but it doesn’t really do anything there. any ideas?

also, while I’m at it, does anyone know of a buna o-ring size from McMaster-carr, etc that will take the place of the nozzle gasket? (part #304940 or #58 in the diagram)

thanks!

[mercuryman]

Think the spring rest on washer other end of spring pushes on Mixture screw plate.

[bbstacker1]

I believe the o-ring you are looking for is #201b

[Mumbles]

The rubber washer seals the hole in the silencer to help make the air go in where it’s supposed to. It helps to keep the intake/reed noise down.

[opposedtwin]

thanks mumbles! so I’m right in thinking it should ride on the barrel of the packing nut, between the threads and the nut end?

[Mumbles]

Exakery! Then the spring pushes it tight to the silencer.

Just thought of something, maybe it was originally intended to stop the paint from getting scratched by the spring. Either way, the motors seem to run fine without it to.

[opposedtwin]

quote bbstacker1:

I believe the o-ring you are looking for is #201b

i was under the impression the size 201 O-rings were for the big twin and RD models. does anyone know if they’re different for the FDs?

i’m pretty sure they are different. for some reason, my notes say the part number for the FD gasket is 302940. I have never seen a parts catalog for an RD or a big twin model with one of these O-rings.

I guess a guy could measure the diameters of both fuel nozzles and see if there is a difference?

[Steve D]

bb is right, 201-B can be used for part numbers 0302984 / 0304940 / 0331181 / 0344037 for 3, 5.5, 7.5, 10, 18 HP. Your notes should say 304940 for the FD, maybe a just a typo, you had it right in your 1st post.

windows 7 screenshot

[opposedtwin]

quote Steve D:

bb is right, 201-B can be used for part numbers 0302984 / 0304940 / 0331181 / 0344037 for 3, 5.5, 7.5, 10, 18 HP. Your notes should say 304940 for the FD, maybe a just a typo, you had it right in your 1st post.

windows 7 screenshot

you’re correct steve, I did have a typo in the 2nd post. any idea as to why OMC has no part number listed for the RD/big twin models?

[Steve D]

I’m totally unfamiliar with the RD/BigTwin series but in looking at a few manuals on Marineengine, unless I’m missing something, the first year I see it is 1961 40 HP, and it’s a different number, #0307778.

[Author]

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