1987 Mercruiser 5.7 Alpha 1 - clank clank clank going in reverse

[Blueghost924]

Hi-
I have a 1987 Mercruiser 5.7 L V8 with the Alpha 1 sterndrive setup. Earlier this year (around June), I adjusted the upper and lower shift cables to the specifications in the book. Going into forward, it shifts just fine, but it's always been "problematic" going into reverse. Up until last month, the sterndrive made a loud groaning noise while shifting into reverse...but it would still go in reverse. Forward always shifted clean with a nice thunk. Now, when running the engine and shifting in reverse, it makes a continuous "clank clank clank" sound. But it does shift into reverse. Yesterday, I watched Chris's video again on adjusting the shift cables, and verified the lower shift cable is exactly 6 inches from the barrel center to the connecting hole center. I didn't not mess with the upper shift cable. Also, the lower shift cable adjusting pin is set to the max height in the adjusting slot. I again ran the engine and testing reverse shifting. Now, the reverse is still making the "clank clank clank" sound, but if i rev it up (jump it up) to about 1200 RPM and back it down quickly, it will shift to reverse and the clanking noise goes away.

My adjustment checks have been done with the boat on the trailer, not in the water. And advice from here?

 

[kenny nunez]

There is a good chance that some salt and marine debris has accumulated in the forward section of the bell housing where the shift slider travels for reverse. You may need a shift cable also, so the drive needs to come off. Sometimes just cleaning and lubricating the slider and the cavities in the drive and bell housing works. When the drive is off and with the cable disconnected in the boat you should be able to move the cable with just 2 fingers in both directions. Any thing more than that indicates a cable replacement.

 

[wrench 3]

The usual problem is the lower shift cable.

 

[achris]

There is a good chance that some salt and marine debris has accumulated in the forward section of the bell housing where the shift slider travels for reverse. ....

That would trip the shift interrupt switch and stall the engine.... He's not stalling, so that's not the problem.

BG... What you are describing is much as I would expect when the dog isn't engaging reverse gear properly. Usually there is a little more movement as the throttle opens and this would account for the proper engagement once the engine speed gets up...

Here's a 'simple' test you can do with the boat on the trailer. REMOVE THE HT LEAD FROM THE COIL TO THE DISTRIBUTOR. With the engine not running, select reverse gear. Do not open the throttle any. Now try to turn the propeller CW (yes, in the forward direction). Now, put your shoulder into it! If it's properly in reverse, it should lock. If it's not, it will jump the dogs and 'click'.

I see you have the slotted anchor pin (on the shift plate) all the way up, so there's nothing left there. If you have watched my shift cable adjustment video, I did a 'slop check' measurement at the beginning. Did you do that? How much 'slop' did you get?

Chris.........

EDIT: Just re-read your opening post... You didn't adjust the remote shift cable. You need to put 4 turns of the barrel in to get it right. With the drive in forward and lower cable on the posts, set the remote cable so it's 'exactly right', then turn the barrel 4 turns AWAY for the end of the cable. This adds a little more travel into Reverse.

 

[kenny nunez]

If after the adjustments are performed and the problem still persists another place to check with the drive removed is the aluminum shift arm where the small rivet holds the plastic wheel, they can come loose even the shift arm screw. The lower end of the stainless shift arm at the bottom of the bell housing may have been distorted at some point when the water pump was replaced because they were not lined up. Does the shift cable from the control box travel a full 3” ? If the control box is a “generic” one and not a Mercruiser that also can be at fault. Is the outer jacket of the lower shift cable not separating? Even where the end of the shift core wire is positioned in the shift slider there could be excessive clerance. What about the bushings in the bell housing that supports the stainless shift arm, that could be loose. Hopefully the shift spool is not the worn or loose. Also with all the poor engagement, the shift dogs are not damaged by now. These are some of the things that I have encountered and worth looking at any time there is an engagement issue.

 

[Blueghost924]

Chris - thanks for the words of wisdom. I didn't do the slop check on the lower shift cable mentioned in the video...that I need to do. Also, I adjusted the remote (upper) shift cable the end of last year, but didn't check it again recently for this reverse problem. That I need to do as well.

Basically, I need to crawl back into the hole (hell hole in the summer) and make sure I check everything!

 

[Blueghost924]

Quick update: Yes, I tried to shortcut my analysis by only checking the lower shift cable. We had a break in the weather this morning, and I followed Chris' advice and readjusted the remote (upper) cable. It's shifting smoother. Chris - if I ever make it to Perth, it's 3 rounds of whatever you'll have that I'll pick up the tab for. Lesson learned: DON"T SHORTCUT!

By the way, my adjustments have all been on the trailer at home. Weather is supposed to be nice tomorrow - should I put the boat in water at the local ramp and re-check the cable adjustments?

 

[achris]

Quick update: Yes, I tried to shortcut my analysis by only checking the lower shift cable. We had a break in the weather this morning, and I followed Chris' advice and readjusted the remote (upper) cable. It's shifting smoother. Chris - if I ever make it to Perth, it's 3 rounds of whatever you'll have that I'll pick up the tab for. Lesson learned: DON"T SHORTCUT!

By the way, my adjustments have all been on the trailer at home. Weather is supposed to be nice tomorrow - should I put the boat in water at the local ramp and re-check the cable adjustments?

:thumb: