Have a 2001 mercury 4 stroke 50hp. Had problems with motor bogging and shutting down at 2500rpms the mechanic replaced the temp sensor and he said that the motor was still bogging at 4500rpms so he replaced the prop.( the old prop had 3 blades the new one has 4 ) Has great power now but after the first trip out I noticed oil seeping at the base of the motor above the propeller, looked like it was coming from the seam that runs down the back of the motor. I wiped the oil off thinking it may have been a one time deal but when I went back the next morning I could see where more had seeped out overnight and left a trail down the fin on the base of the motor. Its not a steady leak but its enough to worry about. Took it back to the mechanic and he says he checked the seals but found no leaks . I know the oil leaked to the bottom of the motor from somewhere I didn't imagine it. Could the new prop be causing too much strain on the shaft causing a leak after its been underway? Any help would be appreciated.
