WARNING-Gearbox drain fibre washers causing screws to loosen

[Nos4r2]

If you've recently put new fibre washers on after a gear oil change on a Yam,a Mercury or a Mariner, go back and check how tight they are.

I recently did my yearly gear oil change, and found my drain and level plugs rather looser than they should be-still needed a screwdriver to undo them, but much looser than I'd done them up to- and a tiny bit of discolouration to the gear oil.

After a chat with the guy I get all my parts from, it appears that both Yamaha and Merc/Mariner have changed the composition of the gearbox drain fibre washers and they compress much more than the old type. He's been seeing the same thing on a regular basis.

So, I went back after a week and retightened mine after this oil change. Shockingly,I got 1/4 turn on it.

[jyasaki]

Thanks, Nos; good to know. I'll pass that one around to my boating buddies.

I'm using a reasonably large stash of washers I got a couple of years ago, so will most likely forget by the time I get new ones...

jky

[Nos4r2]

No worries.
You can tell the old style washers-they are red, but there's a black line round them if you look at the edge. The new type are entirely red.

[Peter_C]

When I was a professional Auto Tech I hated fiber washers and refused to use them, just for the reason that they would come loose (Automotive oil change places use the heck out of them because they are cheap...along with cheap oil filters). Copper works the best, because it has great crush properties (.$$), then aluminum since it is a harder metal. The drain plug gaskets like Toyota uses are a combination of aluminum and fiber and seem to work well.

Fiber washers can also be overtightened easily, causing them to split. There is a happy medium in there, but the recommendation to recheck the torque is probably the best. Thanks for sharing