1981 mc1 mercruiser goes into forward fine reverse is an issue

[merc120_81]

1981 Mercruiser 120 mc1 (mr?) outdrive .

As stated in the topic header, goes into forward nicely, but clacks, doesn't lock going into reverse. I can pull the cable and it will lock into reverse, takes about 1/8" more pull.

I attempted the adjustment procedure, lock into forward, chock the prop, measure to exactly 6" ..... (lower cable)

I adjusted the slide on the shift lever to its extreme, after it wouldn't even get engagement. with the ful slide adjustment.. it gets to the clacking portion of engaging into reverse. I can engaged if I pull the cable about 1/8" more.

Q1) What is the tollerance for play in the lower shift cable, do they actually stretch?? I am just beyond about 9/16~5/8" play.

Q2) Could this be the control. and what is the range of motion for control ( I thought I saw 3" somewhere)

Q4) is it possible that the shift foot is off a tooth.

THANK YOU.

 

[Bt Doctur]

How old is the shift cable? Has the drive been off for service? Did you install a impeller by just dropping the lower?

 

[achris]

Watch my video on adjusting the cable. Questions 1 and 2 are answered in that.

Your question 3 seems to be MIA.

Question 4. No.

 

[merc120_81]

BT: I have owned the boat since 2011, and the cable has not been replaced in that time frame. Boat is run in Fresh Water, and is Trailered
I removed the drive last fall, and replaced the impeller and housing,
I removed the drive, and then split the case.
Shift into reverse was shaky last time I ran the boat prior to the driver work as well. hoped it was adjustment...

ACHRIS, are you youtube chrisa from Australia on Youtube? Excellent video, that is/was my guide for the work, and was .. checking your notes on the specs I was a bit unclear on the 4 turns, away from the cable, is that moving the barrel closer to the end or the sheath?
If I recall correctly, lower shift cable play specs max 9/16" (14mm)
Shift/control cable, travel 3 1/8" , is there any room for error in there? min/max?

because the drive will go into gear with a little extra tug, does that prove out the mechinism/shift in the lower unit?

Missing Q3.. good catch.. frustrated when I wrote the initial.. post. thank you all for the replies.
.

 

[achris]

Me chrisa from Australia? Guilty your honour. That's me.

4 turns towards the sheath.

9/16" is maximum. If the 'slop'/free play is greater than that... FInd it.
Shift cable travel 3-1/8" +/- 1/8".

because the drive will go into gear with a little extra tug, does that prove out the mechinism/shift in the lower unit?

It proves everything is just about right (splines in the right place etc). You could still have excess wear or tolerances to deal with.

Chris...........
(Glad the video is of help )

 

[achris]

OK.. Just to clear up a few myths...

The load on the shift cable isn't even remotely high enough to stretch a STEEL cable... If the loads got that high, you'd be breaking other stuff way before the cable stretched...

What does happen is the inner liner of the cable gets worn, especially on the insides of any curves in the cable, which is why it's critical to set the cable up with the smoothest, biggest possible bend radius, just like it is in the Merc service manuals. When that happens, you'll see it as excess 'slop'/free play when the shift mechanism is 'locked' in one gear or the other.

Excess slop isn't always a worn cable. More likely it one of these....

1. Excess freedom in the shift slide on the bell housing end of the cable. The slide should be free to rotate on the cable, but with an ABSOLUTE minimum of axial movement (we're talking less than 0.2mm)...
2. Wear in the slidefork (where it engages with the upper shift shaft arm roller).
3. Wear in the upper shift shaft arm roller.
4. A loose upper shift shaft arm cross pin.
5. The 'shoe' on the bottom of the upper shift shaft is splayed slightly. (see this one a lot)
6. The foot on the top of the intermediate shift shaft is worn (never seen it, but it's a possibility)
7. Spines in the bottom of the intermediate shift shaft or the top of the lower shift shaft are worn (also, never seen this, but it is a possibility)
8. Wear in the shift crank on the bottom of the lower shift shaft. Splines or the crank itself.
9. Wear in the shift spool.
10. Wear/out of adjustment nut on the end of the spool shaft.
11. Lost tension in the spool spring.
12. Wear in the cross-pin or clutch
13. Wear in the dogs on the gears.. (common with drives that have been 'eased' into engagement.)

I've also seen a lot of bent intermediate shift shafts, which can lead to the shift mechanism binding up.

That just about covers the entire shift path....

Chris.......

 

[merc120_81]

So it sounds like, no matter what, I am pulling the leg off again.
Attack the cable first? Any documents, on tests/tolerances/specs of the rest of the above mentioned wear points? I will probably pull the leg wednesday night. Perhaps some photos are in order.

 

[merc120_81]

Well, I pulled the leg off finally, made some time. then started into the cable replacement only to be stopped, by a siezed cable in the bell housing (unscrewing the cable) I purchased a Sierra shift cable tool (18-9806),and it seems to slip more than grip the cable nut. I am soaking it down in pb-blaster (penetrating oil) and praying at this point. Any good hacks on getting out a stuck cable? Or the best tool for the job?

 

[Bt Doctur]

use a 6 point socket
cut the white plastic tube, hammer on a metric 6 point
drill for 1/4 inch pipe thread and retap with the STRAIGHT TAP

 

[merc120_81]

No Title

Appreciate the advise BT.
I wound up using a blue point 9/16 deepwell extractor available from snap on. Worked like a champ. Installing new cable tomorrow, hope it does the trick for the shift into reverse!

 

[merc120_81]

Closing this one out. Thanks as always iboats community! special shout outs to Achris, and Bt Doc!

Up and running!!!.. and back on the water.. Although I fear, a replace/rework of the lower is approaching fast. Hopefully, not until the winter layup.