Seapadrik;
I keep my tools aboard in mahogany cases. Ordinary steel tools too ... I spray them with WD40 (or similar) and there is practically no rust after many years. There is something about keeping tools in wood cases that minimizes or eliminates rust. Maybe, after many years of use, the oil impregnates the wood or something. Link to a manufacturer of mahogany cases:
Mahogany Cases - Van and Company (Usual disclaimer: I'm not connected to this company in any way ... I just like their products.)
To my way of thinking a sailor can't have too many tools. Last summer two studs holding the heat exchanger to my Perkins 4-108 engine sheared off. I was in New England, over 1500 miles from my home port. None-the-less, I removed the head while at a mooring with the tools I had on board. The head had to go to a machine shop (by dinghy) to have the broken studs removed and their holes re-tapped. When I got it back, the only tool I had to purchase to re-install and re-assemble the engine was a torque wrench, which I immediately added to my on board tool collection.
I like being self sufficient.