95 750 STS New to me

I just got this ski a few weeks ago and it is my first one! I seem to be getting quite a bit of water in the hull when I open the drain after riding it. How much if any is normal? And where would I start to look for it? I dont see an electric bilge pump does it have any kind of pump? Also the prior owner took out the oil tank, so what is the best mix to run 50:1 or 40? One last question, the fuel indicator starts out at full (with full tank) and with in a few min of riding drops to the E. Thanks for any help.