Re: mercrusier 165 wont start
To see if your motor is seized, make sure you are in neutral, pull ALL of your spark plugs out and manually turn the motor (turn the pulley facing the front of the motor). With the plugs out, there should be NO compression, thus making it easy to turn the motor by hand.
You do NOT need to turn the key on. You do not need any kind of power to do this...
Just pull all plugs and (you might need a pry bar of sorts to help), but turn the motor (in the proper direction) by "hand".
If you can, good. If you can't... Seized motor.
To see if there is (a: OIL IN THE MOTOR) - Check the dipstick. If you see brown oil... good. Black... Not as good. Milky... water in oil.
Good luck again!
This is all assuming your starter is working though.