Re: 97 mercury 40 h.p. high rpm low speed
Forward gear has an overrun clutch built into the lower unit that is used when coming off plane where the prop is turning faster than the engine. This overrun clutch disconnects the prop from the powerhead and prevents it from bringing you to an abrupt halt....teeth in windshield kind of thing.
Most regular rotation engines of today are RH meaning that to produce power the powerhead spins the prop clockwise looking at it from the rear of the engine. So, if the engine is stopped, putting pressure on the port/left/traffic side or whatever should meet with resistance. To get the prop to turn the crankshaft would have to turn also. You can test this by just stepping on a blade on the left side and feeling the resistance and if it turns, the flywheel should be turning also.
Conversely, moving the prop by hand CW with the engine stopped and in F gear, will result in a ratcheting action, think about a saw blade in the reverse direction of cutting where the blade is sloped and you slowly ride up a ridge and drop down to repeat the process. This is your over run clutch in action and is used every time you slow down. Prop/propshaft is easily rotated by hand.
A spun hub MAY show up on your initial test where you stand on the prop attempting to turn the crankshaft. It may slip and it may not. If a rubber hub it's hard to tell like that. On a plastic hub, like a lot of props are using now-a-days, with brass insert, remove the prop and look at it. If the plastic is broken or the brass part bent back, you have a spun hub.
When you put on a different prop, did you water test it or just spin it with your hand? If you didn't water test it then don't draw any conclusions about it not making any difference or solving the problem. If your current prop has a spun hub, a water test with another prop would determine that.
HTH,
Mark
