My 2 stroke mercury 150 seems to not be running 100%. I took it in because the warning light was beeping and the water pump seemed to not be pumping. They replaced the water pump and other stuff, 2k later I hit the water and the warning light isn't beeping but it's staying on and not running at top speed. They diagnosed it as the plastic gear that controls the oil flow as being bad. But seeing as the fixed the boat and as soon as I hit the water it wasn't correct I'm not taking there word for it. I don't know anywhere here in SE Michigan I can take it and not get ripped off. But anyway to my question. Can I just mix the oil myself and not worry about the gear? Thanks for any help