Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

[ptj]

Hi All, I've got an older (84) Mercruiser IO with an Alpha drive that has been having shift problems for some time. Original shift problems ranged from the kill switch activating when you gave the boat too much forward throttle to killing the boat in reverse. Since I figured this boat has never had a bellows service I've owned the boat for 20 years and suspect the previous owner never did this either.(he was the original owner). Figuring the lower shift cable needing replacing anyway I dove in a few months ago and replaced all the bellows (man, that was a nightmware), put in a new gimbal bearing (another nightmare as the old one didn't want to come out so had to cut it out), bought an alignment tool and aligned things, and put in a new lower shift cable, new bellows, new gimbal bearing etc.).

After getting everything back together, I can't shift. Basically the same problem as before I started this exercise. Seems like there is something to be learned here about spending more time troubleshooting the actual problem before diving in and replacing things (The old bellows were pristine as was the old gimbal bearing by the way).

Removing the lower shift cable from the engine, I can get this into reverse ok but forward rarely engages. It's as if the cable doesn't have enough forward throw when I shove the cable all the way in . Looking at the shift shaft shoe (under the outdrive), I don't see that it is completely facing forward (appears to be at about 11 o'clock instead of 12 o'clock which is what I'd expect). Hmmm. I did replace the impellor on this outdrive a couple of years ago...it is possible to not align the shift shaft correctly when bolting the lower unit to the upper gear housing? I see some warnings implied to this effect in my Seloc service manual so I'm wondering if maybe all this started when I did the water pump impellor service.

This one has me stumped.

 

[stonyloam]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

From your description I would suspect that the bottom of the upper shift shaft is bent.

 

[ENSIGN]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

sounds like you have the shift shaft off a tooth

 

[stonyloam]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

sounds like you have the shift shaft off a tooth

If it were off a spline, the control would be jammed and you would be stuck in reverse.

 

[ptj]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

Ok, I've got the outdrive off the boat and up on the bench. It shifts FINE! I remain confused. I've got the shift shaft with the shoe facing forward and it shifts into foward gear just fine (same for reverse). My thoughts about the shift shaft being off a spline aren't make sense (besides, the thing shifted fine for quite awhile after the last time i had the lower unit seperated so this doesn't add up).

The cable throw seems to be completely adequate when I manually work it back and forth (with the outdrive removed). When I had the outdrive bolted on, I could only get the shift shaft to about 11 o'clock (needs to be 12 o'clock to be in full forward. Strange.

Pete

 

[stonyloam]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

Now that the OD is off take a look at the upper shift shaft in the bellhousing. Does the bottom point straight ahead? Are the bushings loose? Is the shift lever on top tight? Is the pin holding the lever to the shaft tight? It might be a good time for new bushing and updated seal since you have the od off. Is the wheel on the shift shaft lever securely between the arms of the shift slide?

 

[CaptainMak]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

Did you engage the FORWARD gear before doing the work ?
I just did my bellows also and had to re-adjust the remote control cable to make my reverse work. If you go that route, make sure you remember the original setting.

 

[ptj]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

The upper shift shaft looks fine (no play in the bushings and it moves back and forth just fine). With the cable in forward (pushed all the way in from the engine side), the shift slide moves the upper shift shaft to put the shoe facing forward ok. I'll have to check the wheel again but I think it fits fine between the arms of the shift slide (as long as I don't pull the slide out too far).

 

[ptj]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

Yep, forward was engaged before doing the work (can't remove the OD w/o doing this first and you have to make sure everything is in forward gear before installing the OD back into the bell housing). The cable mechanism does shift the shift shaft correctly but in forward, it can't seem to shift it far enough. In the bench though, I have no problem manually moving the lower shift shaft between reverse and forward and the prop engages/disengages just fine.

When I had the engine running (in the driveway), with the lower shift cable completely removed from the engine, if I really pushed hard on the cable, I could occasionally get FWD to engage. Reverse seemed to engage pretty easily though.

 

[ktbarrentine]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

Just shooting from the hip here (yeah, I know we shouldnt do that), but maybe there is crud in the upper drive recess where the shift slide resides when it is in fwd? Got to be something holding you up from being able to move that slide all the way aft (when the drive is on, since you said there seems to be no problem in either the drive or the shift slide/upper shift shaft while the drive is off).

 

[CaptainMak]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

Yep, forward was engaged before doing the work (can't remove the OD w/o doing this first

You'd be surprised how many people actually manage to do just that: remove the outdrive in neutral or reverse.

Try playing around with the drive cable tube (the one that has a small lock nut holding it). I think you might have some slack in the cable. Uncrimp the end of the inner cable and try turning the tube, barrell and all. See if that does anything.

 

[stonyloam]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

OK seems like the upper is good. Try turning the intermediate shift shaft all the way clockwise. Does it go past 12:00. If it does the top might be twisted.

 

[DaveG55]

Re: Mercruiser Alpha - Not Enough Throw In Lower Shift Cable To Get Into Forward

You'd be surprised how many people actually manage to do just that: remove the outdrive in neutral or reverse.

I'm one of them... I managed to get the drive off while it was in neutral. Not sure how and very glad I didn't manage to bend something important. Like you though I had to readjust the cable a tiny bit to get the drive to go into reverse. I found that my outdrive will not go into reverse if the drive is in the full up, trailer position. It does just fine in FWD, up or down but reverse only engages/locks up when the drive is within the "trim" range, maybe just a little higher.