lower unit


Old 05-28-06, 06:59 AM
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Join Date: Jul 2004
Location: Catskill Mountains, New York State
Posts: 16
Question lower unit

Hi, I have to replace the water pump impeller in the lower unit of my Alpha 1 Mercruiser. I have followed the directions in my repair manual, removed all the nuts etc, but the unit will not drop down. Am i missing something? . Thanks, Don
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Old 05-28-06, 10:24 AM
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Make sure your sift rod is in neutral. Some rods have an "S" shape and if it isn't in neutral, it won't drop. Also, depending on how long it's been since the unit has been dropped, it may be corroded together. Don't be to afraid to give it a couple of whacks with a dead blow or rubber mallet.
Old 06-04-06, 08:39 AM
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Join Date: Jan 2006
Location: North East Ms.
Posts: 122
Alphas need to be in forward to drop drive. If counter rotating then reverse.
Old 06-07-06, 09:55 PM
Join Date: Jun 2006
Posts: 13
If you're trying to drop an Alpha 1 (non gen 2) drive lower unit only, you can theoretically drop it in ANY gear. Most techs, including myself, will usually drop the lower unit when the drive is in forward gear to help with reassembly and shift orientation after a waterpump job, but theoretically, you can drop the lower regardless of what position the shifter is in since the shift shaft (which is splined but straight) will seperate from the shift arm on the upper half of the drive.

If you're trying to pull the complete drive unit from the bell housing, you need to be in forward gear if you have a standard rotation Alpha 1 (uses right hand rotation prop). If you have a counter rotating Alpha 1 (uses a left hand rotation prop) you need to have the shifter in reverse gear.

Make sure you have removed all the hardware if you are having difficulty dropping the lower. The most common nut that people forget is the nut under trim tab anode (remove the trim tab anode and you will see the hidden nut) another one that is sometimes forgotten is the nut in the very front near the shift arm.

There are 6 nuts (not including the anode) that need to be removed before the lower will drop. Due to the length of the studs the two nuts on the side of the drive unit should be removed last (and installed first on reassembly), they will actually help seperate the drive since they cannot be completely removed without pushing upward on the upper drive unit, if you forget to install these two first on reassembly, you will not be able install them without slightly dopping the lower again.

If you are sure you have all the hardware removed, then corrosion may indeed be a factor which would require carefully striking the lower unit with a rubber mallet.

BTW, when reassembling the two drive halves, make sure you install a new oil passage seal (quad shaped oring, usually orange in color) between the upper an lower (this should be standard practice) to prevent any oil leaks between the drive halves.

Good luck,
Old 06-08-06, 03:24 AM
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Join Date: Jan 2006
Location: North East Ms.
Posts: 122
IF you have trouble seperating the drive from the bellhousing take the rams loose, all the hardware (check twice) lift the drive some and put a 2x4 between the outdrive and the bottom of the bellhousing, lift the drive some and let go. It will contact the 2X and jar itself loose from the housing (maybe). IF WORST COMES TO WORST. If you use a screwdriver to try to pry them apart you take a chance of messing up the sealing surfaces.
Old 06-10-06, 01:40 PM
Join Date: Aug 2004
Posts: 25
Try this.

Get some tapered building wood shims for the separation metal to metal.

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