I always run the trim up/down a few times then let it sit for either overnight or till the end of the day. The oil has air in it and foams up. Once that settles out check again. Top off as needed, and check a couple days later to be sure it’s at the correct level.
I try to use marine rated wire for most repairs . And sealed, shrink type connecters. It’s been working well for several years now. Correct running the grounds to each light to. Led lights are perfect for me, but I’m not in salt either.
I think that plate was added at a later time. See the rust on the screws. Myself would do as suggested, put a solid plate on there. Preferably riveted with solid rivits, or have a plug welded in at a good aluminum welding shop.
Any horn is a good horn. Power boats are required to have them, I don't know why a lot of sailboats don't. If it turns foggy it would be a hazard to other boaters to not have one.
Well then it's not a funky repair. You will have to find where it's coming in. Once I worked on one that I couldn't find the leak, But a different setup than that. The forward area was sealed to the cuddy cabin, but the cuddy would get water in it. Food coloring in the area behind the cuddy, and...
Idle it for a few minutes and shut down. My procedure for years, no issues. It gives the motor time to cool down. I always laugh when I see others shut down when drifting into the dock and then the wind gets ahold of them, and they have to re-start. Never shut down at higher than idle and till...