LBD

With regards to a washer.... if the hole the the clevis pin fits through is a good fit then no, But if the fit is sloppy, then use a washer that is a neat fit to the pin. Always us a robust washer with the less sharp edge towards the split pin.

There was a ferro boat in Lytleton in the 70s... on the hard because it leaked so bad, looked like it had been plastered with a shovel, it was as smooth and fair as an elephants hide .... named "Turning Point" very apt as it certainly was for anyone considering ferro construction.

Definitely a positive shift... it is all to common to find some one who is a little timid with the gear shift... yes correct cable adjustment plays a big part of it too.

Huh?...Oh I get you...bit droll.... AS well as being higher tensile, corten is also more corrosion resistant than mild steel, so it has a couple of things gong for it.... difficulty to work with and some what specialty welding requirements, count against it

The sludge tank you refer to is to contain the toxins heavy metals and biocides that leach and wash out of the paint system used, the sludge tank is not to contain the natural organics that you see around mussel harvesters and growing in the bottom of your boat.

slow gear changes are also a cause of damage click.click..click...click....click.....click......click.......click........click.........click..........click...........clunk... if you get my meaning.... a solid clunk is much easier on the box.

If you keep running into dead ends, try http://www.duralloygears.co.nz/ They have made a few specialty gears for me in the past... will not be a budget option but will get you going.