95 C40 Lower Unit screw rusting away

[ncfishhawk]

I have a 95 C40 Yamaha that has been used primarily in salt water but always rinsed out/off. There is/was a screw head located near the front of the gear case that has badly corroded and rusted away. Its not a drain or vent screw. Anyone know what this is for and any idea on how to get it out at this point to replace ? Thanks in advance.

[99yam40]

the only screw on the front is the drain on my 99 C40
a pic of what you think is your drain might help

[ncfishhawk]

It's 15 and 16 in that pic.

[99yam40]

I have no idea what it is for, my C40 does not have that

[ncfishhawk]

based on the pic of the actual screw in the parts listing it has a longer smooth piece on the end of it like it would lock something internally or perhaps something swivels on it. if i was actually able to remove it somehow i'm afraid whatever is on the other end may fall out of place

[boscoe99]

How about one photo showing all of the screws?

[ncfishhawk]

here is pic of the screws below cavitation plate. the oil fill and oil level screws are apparently made of some different type metal that doesn't rust. OB pic 2.jpg

[boscoe99]

It has got me wondering if that is not someone's idea of a repair.

[ncfishhawk]

I bought motor new in 1995. Its been that way since I got it.. The gear case is made to accommodate the screw..ie indented so it fits flush sort of so no way it's aftermarket.

[boscoe99]

What does your owners manual have to say about that port?

[boscoe99]

And 27 years later you are just now questioning it?

[ncfishhawk]

Owners manual says nothing about it and I don't see it on my service manual. I just noticed it being as bad a shape as its in really. I'd like to figure a way to replace it if possible. I'm sure that will be a major task if it's even feasible at this point.

[TownsendsFJR1300]

Sure looks like the LU oil fill screw.

The one way up high, is that not a vent for filling?.. (#16 the fil l plug, #14 the drain plug)..

Also, that part sticking out is likely a magnet.


Part #15 shows a gasket..



https://www.boats.net/catalog/yamaha...casing-drive-1

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[99yam40]

I was thinking magnet also to catch metal from gears and bearings, but I thought the drain screw had a magnet for that.

maybe you can find a good welder to weld a nut onto that screw so you can get it out and replaced.
do the welding on the inside of the nut.
but I am not sure where you should hook up the ground lead

drill and ease out may be the way to remove

[TownsendsFJR1300]

Per the parts diagram, part #14, the drain, doesn't have a magnet. I thought too the magnet is usually on the bottom but it'd still work..

My F150, the magnet is on the bottom drain.




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