A friend of mine who wants to sort it out said to leave it soaking in wd40 for a while?
What is C4
C4 = disassembly aid. After disassembly, the parts that cannot be found will need replacing.
Its an elderly watercooled IC. The fact that it turns and has compression means it can probably be started, but can the watercooling bits be trusted? It could be annoying to have it run out, spring a cooling leak, stop, fill and sink. Broken cooling systems sink real ships, too.
Definitely a candidate for electric, though. With modern gear, much easier to operate and you do have reverse, or, as boaties call it, "brakes". Its probably ply, rather than balsa.