Re: Yanmar 2gm20f
It could be as simple as...the boat is sitting differently in the water. Did you move any heavy gear, fill a tank, or have another person aboard? It doesn't take much to change the oil level slightly due to the angle of the boat.
Otherwise, its either water or fuel. Wipe the dipstick on your fingers and give it a sniff for fuel. If you've got a water leak, you'll see "white smoke" in your exhaust.
However, its sounds like you've got it running again, and with all the stresses of the runaway throttle, it may have sorted itself out. A good remedy for many an old engine is simply a good 24 hour run...gets it fully up to temp, all the chunks can work themselves out, get the grease where it needs to be. Too often, marine engines get run for only 10 minutes at a time, and never get up to operating temps...this is hard on an engine.
I think you are doing the right things....keep changing the oil when its dirty, and keep checking the level. At some point, you might consider going for a sail...LOL!