Alpha 1 gen 1 - sticky lower shift shaft question

Dima_NZ

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Dec 23, 2018
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Hi everyone. My first post here (although I've read plenty of great advice over the years).

Dima’s attempt at a short post to describe a long problem with a 1998 4.3L EFI and a 1988 Alpha 1 Gen 1 lower gear unit on a 1988 SeaRay Seville 18ft kept on a trailer.
  1. Engine dies shifting from neutral to reverse most shifts, even on driveway with earmuffs. If it ever makes it into reverse, shifts out to neutral just fine. Reason - shift interrupt hinge bracket thing flicks down as I try to go into reverse, and stays down - killing the engine (interestingly, I made a "loop" that I can plug in instead of the switch to bypass it - tested it with the loop out on the water shifting into neutral, knowing that I will need to use the ignition key to come OUT of gear, and it still kills the engine mechanically... but that's for another thread perhaps).
  2. 6” centre-to-centre cable adjustment procedure repeated multiple times as per manual #6, no impact
  3. Control cables checked and operate within tolerance in manual (80mm travel from WOT to WOT)
  4. Shifter cable is near new – pulled leg off, it operates super smoothly with no binding or resistance. Routed around the starboard exhaust riser, as per diagram. Nut threaded all the way into the bell housing. No salt build up, still greased up. No obvious water leaks. Bellows relatively new.
  5. Excessive play was recorded with shifter cable disconnected from shift bracket with prop locked in forward (travel of 18mm from interrupter-plate-starting-to-move to interrupter-plate-starting-to-move), spec says should be 14mm or less. I might have been pressing too hard, so might be within the 14mm after all. Went to investigate.
  6. With leg off (upper still bolted to lower), printed out that “degrees rotation” paper template and tested play in lower shift shaft as per instruction – got 12 degrees play exactly, which is right within spec. Shift spool in lower thus seems OK.
  7. The one thing we did notice (my friend Chris was helping), independently of each other, is how much RESISTANCE there is turning the lower shift shaft CCW to put the gearbox into reverse. From Neutral (say, 11 o’clock), I can use my pinky to turn the lower shift shaft to forward (towards 12 o’clock). But massive effort is needed to turn the lower-shift-shaft CCW towards 10 o’clock to go into reverse.
  8. To confirm what we felt, I built a tool (see attached two pictures) – I push the end of the metal ruler to change gears, and record how much flex there is before the lever starts turning. The metal ruler flexes around 2cm before the shaft starts turning if I’m shifting into FWD, but, it flexes around 6-8cm before it starts turning towards reverse.
  9. My theory is that this resistance of the lower shift shaft to turning CCW inside the lower unit is what’s causing the interrupt switch to engage when going into reverse. It can’t be anything else (I think…)
  10. My task is now to flush the lower unit a few times with diesel/kerosene/part oil to try and remove any gunk that may be binding the lower shift shaft. This could be all that’s needed. However, I’m not that hopeful. It may be that the internals of the lower gear unit are toasted.
  11. It doesn’t make sense to me why the resistance of rotating the lower shift shaft is so much greater CCW compared to CW rotation.
Questions – if the above is self-explanatory:
  1. Have I missed any troubleshooting checks?
  2. Assuming the lower gear unit is stuffed, do you recommend a rebuild, or, with a 1988 Alpha 1 – would I be better off buying a new lower gear unit?
Thanks as always, MERRY CHRISTMAS!!!!!!!!!!!!!!!!!!!!!! 😃 😃 😃 Eat lots of yummy stuff, and hope Santa will be nice to you! 😊
 

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achris

More fish than mountain goat
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May 19, 2004
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27,468
You were rotating the propshaft while trying to shift the lower box, yes?

If so, it sounds like something bent in the shift system in the lower box. Pull the lower shift shaft out and check that. If that's not bent, it's internal and if you have the tools it's easy to pull the bearing carrier and then the propshaft. You can then check the shift spool, dog clutch and cross pin. If they are ok, it's the shift crank, and to access that you need to remove the pinion and forward gears.

Chris.........
 

Dima_NZ

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Dec 23, 2018
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Hey Chris. With the lower in neutral, no, I don't need to rotate the prop, as i can go either direction from neutral without turning the prop. ofcourse, if I want to go all the way into R or F, i'll rotate the prop, but I can reproduce the tightness either side of neutral quite easily.

Can the lower shift shaft be pulled "up" without specialist tools? I don't have bearing pullers or any special Mercury tools to do a full rebuild - plus I'd have to check clearances, shaft straightnesses, tolerances etc - and I'm not keen enough to attempt the lower unit rebuild :) It'll be either commission someone to rebuild it with new parts, or, just buy a new lower unit.
 

achris

More fish than mountain goat
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May 19, 2004
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If you remove the bushing at the top, yes, the lower shift shaft will pull straight up. Be careful as it's a splined shaft...

Chris........
 

Bt Doctur

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Aug 29, 2004
Messages
19,092
My guess is that somebody forced the lower unit on to the upper unit and bent something in the lower. You can only bend 2 things. the shaft or the selector "C" item. Create a socket to fit the bushing slots with a disc grinder, remove the bushing, then carefully pull out the shaft. Try not to be too rough

Split the unit and see if the splined shaft turns with no resistance from F to R
 

Dima_NZ

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Thanks guys, wonderful! Merry Christmas :) I'm a happy boater - spending a rainy New Zealand Christmas in the garage getting greasy! "Boating" is 95% fixing, 4% spending $$$$ and only 1% to get some of those life-long "best day" memories, huh? :D

I'll keep you up to date! Dima :)
 

achris

More fish than mountain goat
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May 19, 2004
Messages
27,468
Thanks guys, wonderful! Merry Christmas :) I'm a happy boater - spending a rainy New Zealand Christmas in the garage getting greasy! "Boating" is 95% fixing, 4% spending $$$$ and only 1% to get some of those life-long "best day" memories, huh? :D

I'll keep you up to date! Dima :)

Cheers Dima...

They say the 2 happiest days in boat ownership are the day you buy it, and the day you sell it...

Chris..
 

Dima_NZ

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Chris - heard that one a lot, but - considering I've used the boat probably close to 10 times in the 5 years I've had it, some of the best days I remember has been with a group of friends, out in some distant island you can only get to by boat. I'll surely be happy when I sell it (whenever that may be), but I've had some "happiest" days already :) may be I'm just lucky...
 

Dima_NZ

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BT Doctur - I split the lower from the upper, and will attempt to remove the shaft over the weekend. Could you kindly elaborate a little more on the tool you suggest? I'm very comfortable making one-off tools and "have the tools" to do so. Reason I ask - the shift shaft bushing seems to have two slots at the top, but no "thread" - if I make a [= type tool, wouldn't the bushing simply spin through WITHOUT moving upwards? As in, how do I get the shaft to actually come up without screwing anything up (I'm a master at the latter....). Thank you guys. Here's a pic from today.
 

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Dima_NZ

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AHHH!!!! CRap.... sorry guys - please ignore my post above - after studying the manual photo above, I saw that the bushing IS INDEED threaded - but the lower part below the o-ring, I didn't see that before. All clear then.... sorry.... :)
 

Bt Doctur

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i`ll try to post a pic but you remove the sides of the socket leaving just the 2 spots to fit into the bushing . i also pressed in a bushing for the splined shaft but i have also used a 1/4 drive socket to fit around the splined shaft and insider the socket
 

Dima_NZ

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Dec 23, 2018
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Bt Doctur - sorry, three more questions:
1. Please see the photo below. This is a 24mm socket, and I grind away the black stuff, right? It's deep enough to fit over the spline.
2. The fact that it's a "splined shaft" was mentioned twice here already - what's the significance of this? My understanding is that if I use this "tool", i'll simply be rotating the bushing around the shaft. So unless the bushing is physically jammed/boiled onto the shaft, the fact that it's "splined" is irrelevant, right?
3. Lastly, assuming I get the bushing off, and I pull the shaft up and out, will I be able to put the shaft back down and in into the shifter "C" looking thing? Or, will the "C" looking thing down in the bottom of the lower unit dislocate and fall over immediately, meaning I won't be able to put the shift shaft back into it once I'm done?
 

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achris

More fish than mountain goat
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Bt Doctur - sorry, three more questions:
1. Please see the photo below. This is a 24mm socket, and I grind away the black stuff, right? It's deep enough to fit over the spline.
2. The fact that it's a "splined shaft" was mentioned twice here already - what's the significance of this? My understanding is that if I use this "tool", i'll simply be rotating the bushing around the shaft. So unless the bushing is physically jammed/boiled onto the shaft, the fact that it's "splined" is irrelevant, right?
3. Lastly, assuming I get the bushing off, and I pull the shaft up and out, will I be able to put the shaft back down and in into the shifter "C" looking thing? Or, will the "C" looking thing down in the bottom of the lower unit dislocate and fall over immediately, meaning I won't be able to put the shift shaft back into it once I'm done?

1. yes. Looks good...
2. correct.
3. The shift crank ('C' thing) is on a post in the bottom of the gear housing. Lift the shift shaft out slowly and carefully. If it hooks up as it's leaving the shift crank, then yes, the crank could be lifted off the post and topple. That would require some very delicate 'fishing', or a strip of the housing to relocate it onto the post while still engaging the shift spool correctly.. I've pulled quite a few out and not had a problem, but that doesn't mean it can't happen.

Chris.......
 

Dima_NZ

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Bt Doctur and achris - YOU GUYS RULE! I successfully completed the removal, inspection, grease-up and reinstall of the lower shift shaft today. Everything went to plan! For the next person that gets stuck (pun intended) with a really sticky lower shift shaft, here are a few photos to help you. If you're in New Zealand (by some wild fluke), private message me and I'll send you the special tool.

Basically:
1. Rubber washing that is on top of the bushing (and below the large OD stainless washer) was all mangled and folded in. Plus there was a lot of deposits of fizzed metal and salt. I picked away at those with a tiny flat-head to reveal the grooves for the tool - and to remove what appears is a large part of the oil seal. The spring is still in tact, and the rubber seams OK, but I think this bushing needs to be replaced. I'll order one shortly.
2. After clearing the deposits, I used a cordless impact screwdriver on the highest setting to "ratchet" the bushing out. It was really REALLY stubborn (had no game at all with a breaker bar), so don't be surprised if a lot of WD40 and ratcheting will be need it to get it to budge.
3. I also discovered that if you remove the gear oil drain plug, you can visually sight the shift crank as it moves between F and R. This was SUPER useful when I was pulling the shift shaft up. A few times when I pulled, the shaft would bind to the crank, so I stopped. A few times, the shaft would go up without clinging to the crank - one of these times I did the removal, and the shaft came out nice and easy.
4. Shaft looked really straight, washer and clip just fine. The o-ring was compressed to a 45 degree shape, so I added in a new similar OD and thickness o-ring for now. I plan to replace the bushing anyway, so whatever I had will do.
5. Smeared everything in special lubricant 101 (the expensive Quicksilver stuff), the shaft just dropped back into the shift crank and I torqued the bushing back down to 50 pount feet with a torque wrench, as per manual

End result - after re-installing the shift shaft and bushing back in, I can go between gears by gently twisting the shaft with any two fingers with minimal force (compared to having to use a thumb and a lot of force before). More importantly, beforehand, I could not shift into reverse using the shifter plate bolted to the starboard riser WITHOUT engaging the shifter interrupt (with the remote cable disconnected). There was that much resistance in the rotation of the shift shaft. Now, it's a piece of cake! The gearbox goes into reverse WELL BEFORE the shift interrupt arm starts moving.

I then did a gear-box flush by filling the gear-case with 1 part of 15w40 engine oil and around 2 parts diesel (photos to follow). So this little project is completed and was well worth-while!
 

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Dima_NZ

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So this is my 1 part oil / 2 parts diesel mixture before the flush (ran for around 1 minute total, with a few shifts in/out of netral etc):

Post flush.jpg
 

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