I just bought a new to me boat last Friday. Its got a 200 Merc hanging on its back. The motor idles at 1000 RPM and when you put it in gear either way it grinds. The prop spins a little to fast for being in idel speed. How do I adjust the idle speed on this motor and what rpm do I adjust it to? Will the grinding stops when the idle speed is lowered? Do you think the lower unit is bad? Please response desperately seeking help. Thank you.