bolting up lower unit to upper Mercruiser Alpha One

On an '89 Alpha One 3.0 litre. Helping a friend change out his water pump. Got that done now we're having a heck of a time getting the lower unit to bolt back up to the upper unit. What is the best/proper way to make sure this bolts up correctly with respect to input shaft and reverse gearing being synced up properly?

I've searched the threads here but havent found a clear method/answer.

Re: bolting up lower unit to upper Mercruiser Alpha One

float2 said:

On an '89 Alpha One 3.0 litre. Helping a friend change out his water pump. Got that done now we're having a heck of a time getting the lower unit to bolt back up to the upper unit. What is the best/proper way to make sure this bolts up correctly with respect to input shaft and reverse gearing being synced up properly?

I've searched the threads here but havent found a clear method/answer.

Click to expand...

Is it in forward gear? If not, do so. Then on the top of the lower, make sure the shift mechanism is facing forward. It should now slip on fairly easily. If the shift mechanism moves turn it clockwise and it will lock in.

Re: bolting up lower unit to upper Mercruiser Alpha One

Lock the prop in forward, by turning it CCW and the shift shaft CW. Make sure the controls are also in forward. Then line up the drive-shaft, the water tube and and shift shaft... Slip it up and if the splines aren't quite right, turn the prop CCW, never CW.

Chris....

Re: bolting up lower unit to upper Mercruiser Alpha One

we're having a heck of a time getting the lower unit to bolt back up to the upper unit. What is the best/proper way to make sure this bolts up correctly with respect to input shaft and reverse gearing being synced up properly?

Click to expand...

imho, the best way is to take the whole thing off. upper and lower. then put them together on the bench. it's almost easy to mate the two when on the bench. in contrast, imho again. putting the lower back on the upper with the upper still on the boat is a real challenge. been there done that. repetitively. most painful to do. line all that stuff up, keep it in fwd, etc.

also, be sure the water tube guide is in the lower (installed in the water pump housing), and the water tube in in the water pocket cover in the upper. use some lub on the ends to assist mating.

again. mating the upper to the lower on the bench is a one man job, might take from 1 to 3 tries before ya get it (+ ya can watch the parts mate as they go together). mating the lower to the upper w/ upper still on boat is a two man job at the least and may take many tries before success and you'll be worn out after dong the deed.

also. if ya remove the upper, there's pm you can do while the upper is off. ie. check alignment, lub coupler, check gimble brg. lub ujoints, check for water intrusion into the bellows.

Re: bolting up lower unit to upper Mercruiser Alpha One

float2 said:

On an '89 Alpha One 3.0 litre. Helping a friend change out his water pump. Got that done now we're having a heck of a time getting the lower unit to bolt back up to the upper unit. What is the best/proper way to make sure this bolts up correctly with respect to input shaft and reverse gearing being synced up properly?

I've searched the threads here but havent found a clear method/answer.

Click to expand...

Search the threads some more.... You didnt mention if you have reinstalled the o-ring at the top of your vertical drive shaft. If so, it could be hanging up on the shaft seal in the upper... the current advice is to remove that o-ring and throw it away. Later versions of the alpha drive do not even have that oring groove because of the problems it caused, and it is not necessary because of the lower shaft seal in the upper half of the unit. Also make sure you have a "good" manual with the right instructions. NOT the Seloc or Clymer manuals.... Other than having the shifter lined up properly per the instructions in the book (and in alot of these threads), it should mate right up. +1 to the advice for taking the whole unit off and doing this on the bench. There is soooo much more you can look at and address this way, and it is much easier to see the water tube going into the water pocket when mating the two halves. Also, this is the best way to do the pressure testing you should do before putting oil back in. With the drive on the boat, it is harder to find any leaks in those upper seals. Just sayin'....
Please keep us posted! good luck.

Re: bolting up lower unit to upper Mercruiser Alpha One

ziggy said:

imho, the best way is to take the whole thing off. upper and lower. then put them together on the bench.

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Amen brother!...
And if you don't have a dedicated stand...pick up a B&D Workmate workbench. An Alpha One fits nicely into it, minus the prop. From there you can easily seperate and work on the waterpump, then reassemble the whole works at waist level.

Re: bolting up lower unit to upper Mercruiser Alpha One

ziggy said:

imho, the best way is to take the whole thing off. upper and lower. then put them together on the bench. it's almost easy to mate the two when on the bench. ....

Click to expand...

ktbarrentine said:

.... +1 to the advice for taking the whole unit off and doing this on the bench.....

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Oshkosh1 said:

Amen brother!.......

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Girls!!!

Re: bolting up lower unit to upper Mercruiser Alpha One

Girls!!!

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there ya go with that girls stuff again ....
finesse over force....
+ there's the PM part too. which i learned from you (and others, along w/ the oem service manual)....

Re: bolting up lower unit to upper Mercruiser Alpha One

Agree take the whole outdrive off and service the U-joints and driveshaft splines and check the gimbal bearing and alignment (with alignment tool). When I put mine together I mount the driveshaft housing upsidedown on my bench to put it together, just "glue" in the quad ring and lower shift shaft washer with some grease, pre-position the stud nuts on the sides, piece of cake. In any case make sure the lower shift shaft washer is in place. Good luck.

Re: bolting up lower unit to upper Mercruiser Alpha One

When I put mine together I mount the driveshaft housing upsidedown on my bench to put it together, just "glue" in the quad ring and lower shift shaft washer with some grease,

Click to expand...

i've never tried that.
what works good for me is laying the two halves on the bench. then slowly pushing them together. i have no prop installed and use the inner part of a flow torqueII prop to rotate the prop shaft (with a adj. wrench) into fwd, + to turn the prop shaft to rotate the drive shaft splines into alignment for mating. i find the quad ring stays in place w/o glue, however during assembly, i watch that it stays in place right up to where it disappears when the two halves mate. to ea. his own. i'll bet both these ideas work well. others probably have there own ideas (as we do) as to how it's easiest for them to do the task at hand.

Re: bolting up lower unit to upper Mercruiser Alpha One

Yeah I usually am doing this alone, so always trying to make it easier, for me anyways. This year I made a couple of little wooden blocks to fit between the halves, just thick enough that there was room to get the nuts started on the studs, then pulled the blocks and put it together, no messing around getting the nuts started.

Re: bolting up lower unit to upper Mercruiser Alpha One

stonyloam said:

Yeah I usually am doing this alone, so always trying to make it easier, for me anyways. This year I made a couple of little wooden blocks to fit between the halves, just thick enough that there was room to get the nuts started on the studs, then pulled the blocks and put it together, no messing around getting the nuts started.

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Slip the lower all the way onto the upper. Put the front nut on 3 or 4 threads. Allow the lower to slip back down and rest on the front nut. Put the other washers and nuts on... Do them all up a little at a time..... Finally, put the screw in under the trim tab, put the trim tab on, then fill with oil.... Piece a cake...

Re: bolting up lower unit to upper Mercruiser Alpha One

We just finished this same job and we were having trouble getting it to go together the last half inch. upon closer inspection of the splines they are square cut and my banging around trying to make it go together had created some very small burrs on the edges of the drive shaft spline detectable only by dragging the tip of a screw driver across it. We knocked the burrs off with a little triangle file and it went together like butter.