Mercury 850 1975 yr model prop not turning.

Joined
Aug 27, 2013
Messages
21
I replaced the lower unit on this motor and when I started it up the prop still wasn't spinning. I put it in gear with the motor turned off and the prop locks up in forward and reverse. it spins freely when in neutral. The impeller is spinning as I get water spraying out. I am at a loss as to what to do next. The motor is a good motor otherwise as I have great pressure in my cylinders. Please help.
 
Joined
Aug 27, 2013
Messages
21
Started in neutral, put in forward then in neutral then reverse. SEVERAL times as I couldn't believe what I was seeing.
 

racerone

Supreme Mariner
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Dec 28, 2013
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36,047
What does " replaced " mean here ?-------Is this replacement new to you ?------Bought it used from somewhere ?
 
Joined
Aug 27, 2013
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21
Bought it from a reputable place that tested it out. It is used but they pull it apart and check it out before selling it.
 

flyingscott

Fleet Admiral
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Apr 8, 2014
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7,985
When you put it together did you make sure the shift linkages are are lined up correctly
 
Joined
Aug 27, 2013
Messages
21
No reverse. It had been slipping and finally went out when I was launching it against a strong wind last fall. Had to give it too much gas. I had been babying it with a slow acceleration up till then.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
It is tough to think of a cause for what you report. Is the shift cable moving the linkage? The only other thing I can think of is that the driveshaft broke between the waterpump and the pinon gear, and the pinon gear is seized. Not your normal situation.
 
Joined
Aug 27, 2013
Messages
21
I check the cable and it is moving the linkage. I'm taking the lower unit off and rechecking how I installed it. I talked with the place I bought the unit from and they said the same as you only that the pinion gear somehow got stripped. I am also going to drain the unit and recheck for any signs of metal shavings.
 
Joined
Aug 27, 2013
Messages
21
So...I took the lower unit off the motor and put it into gear. the drive shaft spun freely and no prop movement. I spun it in forward, neutral, and reverse. I had the same free spinning shaft. Taking the unit back to the place to get a replacement. I'll be checking this one more closely no that I've had this issue.
 
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