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79 Mercury 140 hp Lower Unit

T

tlt2

Member
Got my boat on the lake over the weekend and I have a problem. Runs and does great in forward goes in neutral just fine but reverse a different story. I can shift to reverse and goes in just fine and if I give it any throttle at all then it starts clicking and grinding. I originally figured cable needs adjusted but that's not it. The linkage up top inside the motor housing if moving to reverse as far as it will go and cant go any further. So what's everyone's thought.
I'm thinking one of three thing since the motor is new to me......I'm thing the guy that just put the water pump in may have shift shar one tooth off on the shift rod? If that's possible
OR shift cam wore on the reverse side maybe?
OR the reverse gear bad....what do you all think?

Also what size motor and year lower units will work on my motor
79 Mercury 140 inline 6 cylinder serial number 5433673
 
Shifter splines and probably not aligned correctly last time the LU was removed to change the impeller.

Jeff
 
Dropped the lower unit yesterday and the shift splines being misaligned does seem to be the problem. So now I'm assuming the clutch dog will be my next step.
 
No-----Put the lower unit in neutral.-----Put the control box in neutral.---Now assemble.--------Or put lower unit in forward and control in forward and assemble.--------The spring loaded clutchdog often jumps into forward when you are not looking !----That leads many novices to pull their hair out !!
 
And some of us don't have much hair left!

I recommend using forward since a slight bump and shift it from N to F--and that can remove even more hair

Jeff
 
I did that yesterday.....no change. Notice also that I have a quarter to 3/8 play when I push in on the shape. That's probably a little much isn't it.
 
I'm pretty mechanically inclined and isnt my first rodeo of having s lower off. I've even went as far as pulling my shifter box out and checking it and have also replaced the cables. But any how once you put it in reverse and give it throttle and it start grinding ,clunking ,slipping or whatever you wanna call it. It also acts like the lower is wanting to bind up and is hard to get back out of reverse
 
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No water just change lubes in it. If I push in on the prop shaft and let it go has play on it. No play pulling out just in. If I take my hand and push in word on the prop shaft it moves inward a 1/4 to 3/8 of an inch but with a spring loaded pushing it back out.
 
No freezing weather I'm in missouri. Been in the 60s and 70s for the last 3 months and it was in my garage all winter.
 
That is way too much endplay.----No wonder the clutch dog can not reach reverse gear.------Take this lower unit apart for inspection. ---Something is amiss in there.
 
Took the lower apart today and what I figured out was the carrier housing was pretty wore causing to much end play and letting the clutch not engage far enough into the reverse gear and rounded off the corners on the clutch dog. Also the little shift rod that pushes the clutch dog back and fourth was a little wore also so I swapped the shaft and carrier from a 77 115 and put on it.
 
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