'O' Ring Fell Out of Alpha One Gen II Lower Unit

[mikedj]

I am changing the impeller on my 2005 Alpha One Gen II stern drive. This is the first time I've done it, but the previous owner said he changed it in 2009. When I removed the lower unit, an 'O' ring fell out of the upper housing. I didn't see exactly which cavity it came from, but it was towards the front. It measures 1-3/8" ID and 1-5/8" OD. Looking at the Mercury Parts diagram, the only one I can see that looks like it might resemble it is for the drive shaft housing cover (O ring part number 32546). However, the diagram does not give the dimensions of the 'O' ring.

Frankly, the O ring appears as though it might not have been 'in use'. It is covered on one side with oily dust, as if maybe it was just laying around for a while. But, of course, I would like to be sure of that before reassembling the drive.

Does anyone have any ideas on where it might go?

Can I safely remove the drive shaft housing cover to check for the presence of the cover 'O' ring? Will I mess up any alignments or anything by simply removing the cover (and will I need a new gasket)?

Thanks for your assistance.
Mike

 

[magstang1]

There is an o ring like you describe that is for the water passage. If I remember correctly, there is a depression on the upper right corner where the o ring sits. Smear some grease there and stick the o ring in it, then slide the drive on.

 

[mikedj]

There is an o ring like you describe that is for the water passage. If I remember correctly, there is a depression on the upper right corner where the o ring sits. Smear some grease there and stick the o ring in it, then slide the drive on.

Are you talking about the one I have circled in red in this drawing (this one's on the left, not the right)? That looks like it could match the O ring that fell, but I didn't remove the drive shaft housing from the bell housing, so I didn't expose that O ring.



I only took the lower gear housing off, the stuff in the following drawing.

 

[Last Dollar]

You must be referring to item 12 in the upper drawing, it seals the drive shaft (necessary but not life threatening). The item that will get you in trouble quickly when removing the lower case for water pump service is what appears to be item 7 on the lower drawing. This seals the lower unit oil passage between the upper and lower cases and MUST be in place. I usually put a slight amount of gasket seal on this small o ring to keep it in place until all the bolts are tight. This seal is very important.

 

[mikedj]

You must be referring to item 12 in the upper drawing, it seals the drive shaft (necessary but not life threatening). The item that will get you in trouble quickly when removing the lower case for water pump service is what appears to be item 7 on the lower drawing. This seals the lower unit oil passage between the upper and lower cases and MUST be in place. I usually put a slight amount of gasket seal on this small o ring to keep it in place until all the bolts are tight. This seal is very important.

Item 12 in the upper drawing is a clip. As near as I can tell, item 4 in that drawing is the only one in that drawing that resembles the one I found.

I appreciate the comments about item 7 in the lower drawing. I indeed made sure that I installed that one (having read that it is easy to forget and very problematic).

I tried to post a photo of the one that fell out, but the forum software won't except it (I need to find out what the image limits are).

Thanks,
Mike

 

[midway]

Host your photos on photobucket and then link them here, much easier. Item 12 in the top of the lower drawing goes in a groove on the shaft just below the splines.

 

[Last Dollar]

Since the upper gear case is not shown in either of these drawings we have been overlooking the fact that the item 12 is part of the bearings and seals located under the water pump assembly. Look closer at the dotted lines that show how all these parts go together. Item 12 probably is a clip. However like another contributor stated, there is a groove in the drive shaft, above the water pump housing assembly that has an O ring and keeps moisture from intruding the splined shaft. The diameter of this particular o ring would be very close to the diameters you stated in your initial post. If this o ring was on top of the water pump housing area it has to be from the shaft, probably pulled off or someone left it off on another water pump replacement procedure. Go to a Mercruiser parts web site and check the parts for a water pump replacement kit (which will include the o ring in question) or check the upper gear case diagram to see this o ring.

 

[mikedj]

Host your photos on photobucket and then link them here, much easier. Item 12 in the top of the lower drawing goes in a groove on the shaft just below the splines.

Item 12 in the lower drawing is listed as a Shim. Item 21 is an O ring, but its size is listed as 2.175 x .175, which is bigger than the one in question. It's also below the Carrier Assembly, which I did not remove.

Here's an attempt to upload the photos using Photobucket. Note the amount of dust clinging to it. And on the flip side, some curious white marks, as if maybe it was clinging to some corrosion. In other words, I'm still wondering if this thing was dropped during some service and has been trapped somewhere for a while.

Mike

Mike

 

[mikedj]

Since the upper gear case is not shown in either of these drawings we have been overlooking the fact that the item 12 is part of the bearings and seals located under the water pump assembly. Look closer at the dotted lines that show how all these parts go together. Item 12 probably is a clip. However like another contributor stated, there is a groove in the drive shaft, above the water pump housing assembly that has an O ring and keeps moisture from intruding the splined shaft. The diameter of this particular o ring would be very close to the diameters you stated in your initial post. If this o ring was on top of the water pump housing area it has to be from the shaft, probably pulled off or someone left it off on another water pump replacement procedure. Go to a Mercruiser parts web site and check the parts for a water pump replacement kit (which will include the o ring in question) or check the upper gear case diagram to see this o ring.

Here is the drive shaft housing. In the first image, item number 5 may be the seal you are referring to that fits the groove of the shaft. If so, that's actually a seal, which I did verify is in its proper location.

Mike

 

[Lazy Daze]

You only removed the "foot" (lower half of the lower unit), right? That's all you need to do for the impeller change, anyways. Assuming that's the case, you're correct to think that the o-ring in question does not go to anything. Removing the lower unit and the impeller would not expose any type of o-ring like that.

 

[mikedj]

You only removed the "foot" (lower half of the lower unit), right? That's all you need to do for the impeller change, anyways. Assuming that's the case, you're correct to think that the o-ring in question does not go to anything. Removing the lower unit and the impeller would not expose any type of o-ring like that.

That is correct, only the lower foot. Thanks for your comments and confirming that it shouldn't be there. So, it must have been left during a previous service of some type. It was either replaced, or fell out when putting it back together. If that's the case, the only way I can think of to know for sure is disassembly of the rest of the stern drive. But I've seen no other symptoms of anything wrong in the 30-40 running hours since I bought it, so I think I'll take a wait and see approach. When I get it running again on the trailer, I'll look very carefully for any signs of leakage.

Thanks for all of your replies. It has been very helpful.

Mike

 

[magstang1]

No doubt. That is #4 from the parts list you posted.

 

[mikedj]

No doubt. That is #4 from the parts list you posted.

I agree, that looks like the most likely culprit. But I can't tell exactly what it seals. Is that a water passage? And if there is no O ring there, what would be the nature of the leak? I assume it's intake water going towards the engine, is that correct?

Mike