I started my boat out of water, with muffs on, to make sure it was pumping water. It is. Runs great at idle. nice and smooth, but loud because the exhaust comes out the prop. Anyways, when put it in gear, and throttle it up to about 2000 rpm, the engine vibrates. Now I have a 1/4" chunk out of one of the blades of my prop. Can this cause it to vibrate even out of water? I assume it stil would because it is out of balance. By the way a new prop is on the way.
Also, how do i adjust the idle of my 1970? mercruiser 120?
Yes that will cause vibration and also when you hook up the ear muffs to check your water pumps it wont work. When you put 45psi hose to engine it does need the pump. Your impeller or water pump could be still be bad.
When your boat is in the water then the impeller in the lower unit feeds the water pump on the engine.
The only way to test the pumps is in the water. Watch your guages, if it runs normal temp your fine if you run a little hot then probably your impeller in the lower unit is starting to go and will need changing sooner than latter.