Shifting prob/Alpha I

[nola mike]

So i have a slight issue with the shifting on my new-to-me mercruiser i/o, which i thought was just a simple adjustment (maybe still is, i just can't figure it out). when i'm in forward, i need to move the shift lever slightly into the reverse position to disengage. all gears shift smoothly. i've read through the stern drive manual, and haven't had much luck. also, i haven't been able to find a "how-to" on this forum, though i'm sure i'm just missing it.

perhaps someone can fill me in on my knowledge of the shifting mechanism--maybe the adjustments will make more sense to me.

as i understand it, when i shift into gear, the shift cut out engages, along with movement of the shifter cable. as the handle is moved, it appears that there's a "shock absorber", whose job is to move the shift interrupt switch back to the neutral position.

as i said, i tried the book adjustment. here are the problems i'm running into:

there is no mention of adjusting the actual shift cable, though there is an adjustment barrel on it. how is this done? i would think that this would be the adjustment that i would want to focus on, but have been having a hard time getting it right.

the remote shift cable's length seems mainly to determine the relationship between throttle opening and shift cable movement; ie, when the cable is shorter, the throttle tends to open before the clutch engages.

if i manually activate the shift interrupt switch, i'm assuming the motor should stall--mine doesn't seem to do anything, though as i said, it shifts smoothly out of gear.

i'm wondering if i just have a worn cable/need lubrication somewhere/something else instead of a simple adjustment. oh, everything shifts fine when activating the cable by hand.

 

[jaxnjil]

Re: Shifting prob/Alpha I

NM; you are corect in your assumintion with the shift interupt switch.
when you move it by hand it should kill the motor
i just had this problem on my alpha and wasnt able to get the mircro switch that was on my style shift plate. i had to but the updated shift plate with the plunger type switch.

mine wouldnt shift out of forward or reverse with out over shifting the other way or shutting the motor off

this fixed my problem but there is a better disctiption of this system in the adults only section at the top of this section if you havent found it yet

 

[nola mike]

Re: Shifting prob/Alpha I

yeah, i've seen the sticky. when you over-shifted to get out of gear, was it smooth? i'll check out the switch this weekend--i'm trying to see if my switch probs are related to the apparent adjustment prob.

 

[Fishermark]

Re: Shifting prob/Alpha I

You can adjust all you want, but if your shift interrupt switch isn't working, then you will constantly be fighting with it to get it out of gear.

 

[nola mike]

Re: Shifting prob/Alpha I

yeah, it's an alpha, but i guess that my thinking is that a prob with the SI switch would show up as difficult/hard shifts into neutral. my clutch disengages smoothly, but i need to move the lever somewhat past the neutral position. when i shift out of reverse, all is well. at any rate, i'll fix the switch first and see if that helps the problem.

however, i'm still looking for answers to the original questions:
how is the shifter cable adjusted?
is my explanation of the shifting components/mechanism correct?

 

[jaxnjil]

Re: Shifting prob/Alpha I

mike; i'm not sure how to answer your cable question. after i changed the shift plate on mine i ran thru the adjustments in the manual and mine worked fine

as far as the travel problem it would pop into the gear on the shifter was on with the little grind you allways get. if i could pop it realy quick i could get it back to neutral but easier to shut off motor. i didnt run it long that way and change out the switch as soon as i could.


the one thing i see wrong with your understanding is; you state-- as i understand it, when i shift into gear, the shift cut out engages, along with movement of the shifter cable.--

the only function of the interupt switch is to cause a blip in the power flow to the drive allowing the one way clutch dogs in the lower unit pop apart and let you go to neutral

 

[Kim1349]

Re: Shifting prob/Alpha I

Adults only section??? Huh... I don't see that anywhere. What am I missing?

 

[gmac316]

Re: Shifting prob/Alpha I

I am encountering a similar problem, I had the cable replaced last year from the shift plate to the lower unit. Late in theseason started having issues again so, like an idiot I messed with it and seemed like I adjusted it correctly. Well once this came about I replaced the other cables from the stick to the throttle and shift plate. It still doesnt seem right that I have to over shift. I do remember reading something (I thought was on here) on measurements for setting the shift cables. Any help would be great and save me a trip and money at the mechanics. Thanks

 

[nola mike]

Re: Shifting prob/Alpha I

OK, so i finally figured all of this out. hopefully this info will help someone. my u-joint bellows sprung a leak at the time this was going on, so i figured that i might as well replace the shift cable while in there. short story is that that was indeed the culprit. while i didn't feel that the old cable was particularly difficult to shift, with the new one in, there's very little resistance at all--it should feel just like you're shifting with the cable only (ie, the drive doesn't add much/any resistance to shifting). so, here's what i learned:

1. here's my new understanding of the SIS mechanism: basically, the shift plate/switch only engages when the shift cable encounters resistance. when you shift into gear, or out of gear with the transmission unloaded (motor off, or maybe idling on muffs), the cable offers no resistance. so the switch plate doesn't move, and the remote and shift cables move in tandem. the only time there should be enough resistance to move the shift plate is when coming out of gear--there are good explanations of the dog clutch mechanism elsewhere. the bottom line is that coming out of gear offers resistance. at that point, the remote cable is moving, but the shift cable isn't; ie, they are no longer moving in tandem. this causes the shift plate to move and activate the SIS. this cuts power to the motor, unloads the transmission, and allows the shift cable and remote cable to sync up again.
2. if you can't adjust it, it's your shift cable. as a corollary to #1, it seems that if the switch ever engages when the transmission isn't under load, then the resistance of the lower cable is the culprit, rather than an adjustment. particularly if it happens going INTO forward/reverse. i don't know this for sure, but it seems likely. someone correct me if i'm wrong on this.
3. replacement of the cable isn't hard. hardest part was getting the lower unit back on by myself. special tool/socket: this was the hardest part, but ended up being no big deal. searches on this showed that potential problems included the wall width of the socket and the depth. to me, it looked like socket depth was the only problem. the cable exits the middle of the nut that needs to be screwed in the housing. the problem is that the socket needs to be long enough so that it encloses the length of the cable.
3a. i used a kobalt 1/2" drive 9/16" deep well socket from lowes. it's BARELY long enough to get the job done: the driver won't get in there much, but it's enough to turn the socket. there's no problem with taking the old cable out, since you can cut the cable and fit the socket all the way on the old nut--this lets you get a good grip on it. on installation, you don't need to apply a lot of torque to this nut, so i didn't need a great grip. however, other ideas that would have worked included:
3b. welding 2 sockets together
3c. grinding slots into the socket, allowing it to be turned with an open end/crescent wrench (like a spark plug socket). i was going to do this if i had to, since it only requires a dremel.
3d. cut a notch/hole in the side of the socket, allowing the cable to exit. if you've seen an o2 sensor socket, you know what i'm talking about here.

realistically, if you've never done this before, i'd say about 3-4 hours for the job. i had never messed around with the lower unit, and it took me 5 hours for everything, including the u joint boot (that was harder). it would be much quicker if i had to do it again. it shifts SOOOO much better now, i'm very pleased. i was so excited by hearing the engine blip going into gear--my wife was underwhelmed. anyway, the correct adjustment for the shift cable is 6" from center of adjusting barrel to center of mounting hole with shifter in full forward gear, propeller locked (although i had to mess with mine a bit to get it into forward gear reliably).

sorry for the long post, but this stuff's obvious once you see it working and get it apart, but i hadn't seen a post addressing the specifics above...