I have a 7.5 merc from the 1980s that i just replaced the impeller on. after I put the lower unit back on I wanted to see if the propeller turns by hand in any gears. In neutral it spins freely which is good. In forward it spins clockwise with the ratcheting noise and wont turn backwards which is also good. BUT, when I put in reverse gear and try turning it by hand it wont turn in either direction...is that normal for this motor?