'76 Mercruiser shift cables

italianstal27

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Feb 18, 2017
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Hi all,

S/N: 4445247 (Mercrusier R Drive)

Apparently '76 was the year they shifted from a 5 7/8" lower shift cable adjustment to 6". The previous owner appears to have mixed and matched hardware. The current lower shift cable uses a brass cylinder nut to anchor in place.

Which length would you recommend setting the cable at?

Thanks,
-John
 

Bt Doctur

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Aug 29, 2004
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a brass cylinder but should use a cotter pin to retain it in the housing
Usually I put the control box in full fwd ,attach the plastic end to the stud and adjust the barrel to fit. Then check reverse and adjust the movable stud for proper operation
 

italianstal27

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The moveable stud is the plastic one yes?

Do you ever move the lower shift cable attachment point up and down? There is a slot in the aluminum.

-John
 

kenny nunez

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Jun 20, 2017
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You move the stud up after shifting to reverse and have someone rotate the prop to be sure it is fully engaged. Those service manuals were printed for when every thing is shiney and new not used and old. Do it just as the Dr. described.
 

italianstal27

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In forward or reverse gear were getting a pretty noticeable clunk as we turn. Not smooth at all. Should it be that clunky?
 

Bt Doctur

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In forward or reverse gear were getting a pretty noticeable clunk as we turn.

?As you turn what?
Alpha drives need to shifted briskly into gear.the initial clunk is normal
 

italianstal27

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Ah no we're just spinning the prop, in reverse gear, with the engine off. It locks clockwise. How hard should it be to rotate counter clockwise?
 

Bt Doctur

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thee is no need to rotate it backwards your just looking to be fully locked CW for reverse and no clicking in neutral
 

italianstal27

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No clicking in neutral... It locks correctly in forward and reverse.

But should the prop, in forward, spin freely clockwise? Require 2 fingers to move it? 2 hands?

Phrased differently, how difficult should it be to move the prop in the correct direction?

Thanks,
-John
 

Bt Doctur

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freely if the cable is not connected to anything and you rotate the prop shaft
if the shift cable is connected to the control box there will be a ratcheting sound as you turn the prop F is locked CCW and ratchets CW
R is locked clockwise and ratchets CCW
 

italianstal27

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Brilliant, ok so here's where we're at...

I can adjust the forward motion to spin freely, however, when shifting into reverse, the CCW motion is very very clunky. Requires two hands to rotate.

There is 3" of travel on the upper shift cable. After playing with the lower cable, by hand, it seems that pulling it all the way extended actually makes it worse. If I had 2.5" of travel on the upper shift cable things would be smoother.

Going in the other direction, pushing the shift cable into full forward makes it very very clunky. The sweet spot seems to be: Push lower shift all the way in while friend counter rotates prop, then pull cable out 1/4".

Does that make sense? At what point do you "set it to spec and turn the engine on?"

Thanks,
-John
 

Bt Doctur

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your overthinking it, remove the lower cable, shift into full forward, full throttle. attach the lower shift cable to the stud, adjust brass barrel to fit. retest and report. From the video it seems there is too much travel/tension when in reverse.
 

italianstal27

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Alrighty! Got it shifting nicely *we think*


I had shifted my tachometer to position 1 for 4 cylinder engines, but now it's saying we're running at 200 RPM... which is obviously wrong... So I'm not 100% sure what speed the engine is idling at.

is the best method for checking to use an inductive lead on cylinder 1 to verify the tach?
 

italianstal27

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Ahhh also the trailer is buzzing. That's the metalic clinking sound -.-

Let me knwo if there's any good that can be pulled from this video. Otherwise we'll shoot a new one. Man that's frustrating :(
 
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