Back to square one. merc LU

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Lostfisher

Petty Officer 2nd Class
Joined
Nov 2, 2009
Messages
147
well i changed the propshaft on a merc 18hp. the last one was bent. after i got it together it was running really rough. so i took it back out of the water and saw lots of shavings on the magnet screw. any idea on what could be happening it actually sounds like it was trying to engage while running. i have not taken the lu back apart to see what is grinding yet. but i am becoming very frustrated very quickly with this motor.
 
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Moody Blue

Captain
Joined
May 24, 2004
Messages
3,136
Re: Back to square one. merc LU

Lower units are not to be taken lightly. They may seem simple but a very high degree of precision is required to prevent them from self destructing.

Gear preload and backlash settings are adjusted in the 0.001" range. Too little or too much and the gears will grind themselves apart. Did you have a manual when you replaced the shaft? Did you follow the backlash setup procedures?
 
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Mi duckdown

Commander
Joined
Apr 14, 2007
Messages
2,575
Re: Back to square one. merc LU

What Moody Blue. Posted
Did you put the NEW Propshaft on V blocks to see if it was TRUE.
To many variables.
GOT TO ASK? How did bend the prop shaft?
And yes a dial indicator is a needed
 
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Lostfisher

Petty Officer 2nd Class
Joined
Nov 2, 2009
Messages
147
Re: Back to square one. merc LU

no I did not put it in a v block it was brand new. the propshaft was bent by hitting an underwater object. I thought that there was suppose to be shims for the backlash setting. do you know f any how too's on here for me to reference??
 
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Mi duckdown

Commander
Joined
Apr 14, 2007
Messages
2,575
Re: Back to square one. merc LU

And you have an OEM merc service /repair Manual For that Motor?
 
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Lawnmedic

Seaman
Joined
Jan 22, 2011
Messages
60
Re: Back to square one. merc LU

Lostfisher said:
no I did not put it in a v block it was brand new. the propshaft was bent by hitting an underwater object. I thought that there was suppose to be shims for the backlash setting. do you know f any how too's on here for me to reference??
Click to expand...

Go the the first thread at the top of this forum "FAQ For Mercury/Mariner Outboards " Don has a link that will take you to shared files where you can download the factory manual you will need.....
 
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Lostfisher

Petty Officer 2nd Class
Joined
Nov 2, 2009
Messages
147
Re: Back to square one. merc LU

Do u guys think it could be because I didnt torque the carrier bearing down enough.
 
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Moody Blue

Captain
Joined
May 24, 2004
Messages
3,136
Re: Back to square one. merc LU

Absolutley. Same as driving your car down the freeway with the wheelnuts only spun on loosely. Wheel will stay on for awhile then start to wobble then fall off completely with catastrophic results.

That carrier nut on my 80hp Merc requires it to be TORQUED to 250ft/Ib. Not sure about the spec on your unit.
 
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