Reverse acting weird

[sti1471]

I have a 1984 Mercruiser 140 3.0L, connected to an Alpha MC1.

I had the lower shift cable replaced by a marine shop. the outdrive fluid is full and water free. I had the boat out at the dock yesterday to test everything and I noticed something weird. When I shift into forward gear it goes in and everything seems to work just fine. When I shift into reverse gear, it will go in, but after about 2 seconds, it makes a weird noise. The best I can explain it is that it sounds / feels like the prop is hitting something under the water. About every 1 second, bang, bang, bang. Kind of like it is slipping out of gear and back in gear.

If I go back to the engine and shift it into reverse manually, and hold the shift lever tight, then it does not make that noise.

Not sure if this helps or not but when I got it back home, with the engine off, I shifted into forward, and the prop was locked.
I then shifted to Neutral and it was free spinning both ways.
I then shifted it to reverse and the prop was locked as it should be. HOWEVER, The prop has about 1/4" of back and forward play. I have heard this is normal but when I pull the prop back (away from the boat) the prop then almost locks but it will slip and I can turn the prop. I push the prop forward into the drive and it prop is locked and will not turn.

So when the boat is in the water, if I put it in reverse, then the prop naturally pulls away from the boat and I wonder if this is where it is not locking.

If this sounds to be the case, then what seems to be wrong in the outdrive that 1/4" movement in the prop would cause this? I have replaced the shift cable, and the shifter at the helm, and the lower shift shaft. The only thing I have not replaced is the control cable. That might be next.

 

[camalot]

It just needs adjusting for the reverse action , quite simple. At the end of the cable where it attaches to the pin this can be adjusted. Simply loosen the bolt at the end of the pin and move the pin up a little, this will give the cable action the length it needs to go into reverse.

 

[sti1471]

I do not recall the slide setting off the top of my head, but I thought I remember raising it last season. It might have slipped back down or something. However if it did not slip down and the slider is already at the top position, what then?

 

[camalot]

Take it back to the shop that fitted the new cable, if the pin was fully adjusted before the new cable they may have adjusted it down when fitting the new cable. You can if needed go out of the factory spec a little to get forward and reverse.

Remove the cable from the locating pins....stick it into forward gear (with someone turning the prop counter clockwise) and check the hole centers, should be 6"

 

[sti1471]

When I first heard the problem the first thing I thought was that the clutch dogs might be messed. But if I can hold it with my hand, then that should not be the case. is the control cable is stretched or needs to be replaced could that be causing this?

 

[camalot]

The remote or the shift cables tend not to stretch........they tend to go stiff.
The remote cable should have 3" of travel,

Google "mercruiser shift cable adjustment" loads of pic's even a manual online and a youtube how too.