When I had my 90 2-stroke, my low oil sensor would start to beep at the 1/3 mark on the tank. It would beep during the holeshot because of the angle of the engine and then stop but it would churp if you hit large waves or when you started to come down off plane. Used to scare the crap out of me all the time then I started keeping it almost full and the problem went away even if I didn't refill it after a couple of trips.

Other than that you have electrical issues (duh lol). At this point if I were you I would set aside one weekend and replace every terminal end you have in the boat with a marine grade, waterproof terminal that has the heat shrink feature. I would start with the main power cord by making sure it's properly tinned and the battery posts are clean then I would start replacing each end, one at at time until you knew with absolute certainity that you have good, waterproof connections everywhere. Those ends are expensive but well worth it. You have been fighting electrical issues of some sort since you have owned the boat. It's time to take a weekend off from fishing and fix it properly once and for all. Just my two cents.