When it is on a hose or trimmed out of the water there is NO LOAD on the prop.-----It will bark and roar on 3 of 6 cylinders.------Checked reed valves ?----Perhaps pistons are not installed correctly ??
On a fresh water motor they usually come out no problem.----Done more than one 67 tear old motor.-----Pouring boiling water over the block/cylinder head area will heat the area of the threads.---Expands the aluminum and releases the grip.
Folks today know little about mechanical things.----Do you see folks lifting the hood at the gas station to check oil ?----Or it costs too much to have the local boat shop do simple stuff like a lower unit reseal, I think.
