Alpha One Gen One, Upper Drive shaft seal,

[PETCH]

Hello,
New Boat Owner here: 1986 16' Peterborough Monza with a MCM140/Alpha one. The Alpha One, Gen one, is leaking oil from the Weep hole. So I am replacing the Shift Shaft seal and bushing, along with replacing the Impeller, gaskets, and both the top and base of the Impeller housing. I will pressure test unit before re-install.
My questions are in regards to the vertical Drive Shaft. With this older drive, I have the O-ring groove just below the spline. When I removed the lower unit, I found this O-ring had come off and was sitting up in the Upper Unit where the Drive Shaft seals are. I also found what appears to be another piece of a similar size O-ring up there. Must have been from prior owner.
Q: Do I install the shaft O-ring or not? I have read yes and no.....

In the Upper unit, where the top of the verticle drive shaft slides into the Upper unit, there appears to be 2 seals. I'm trying to interpret the drawing in the link:
http://www.iboats.com/Mercruiser-St...8891364--session_id.577619652--view_id.272967

Q: What seals are used to seal the verticle drive shaft in the Upper Unit? Is there suppose to be an O-ring up in there in addition to the O-ring on the shaft?
part numbers 14 and 13 appear to have different ID's.......

Q: Can these seals be replaced from underneath?

thx
Petch

 

[ziggy]

while i'm not the pro here. but i do have some input.

as to the oring on the vertical shaft of the lower. no, ya don't use it. proof that ya don't use it is if ya were to buy a replacement vertical lower drive shaft, it would come w/o the oring groove. so ya couldn't install that oring. i have the oring groove and have not used that oring for years w/o ramifications.

as to the bottom two seals in the upper. the very bottom seal can be replaced from the outside, with the upper separated from the lower ya can see it, remove it, and replace it. the other seal is done from the inside of the upper. the vertical drive shaft is removed to go get that seal. i've done the lower seal a couple times, the one above it i haven't done. i think it may take special tools to remove and replace it.

i'm not aware of an oring in the upper, except maybe the top cap uses what looks like and oring for it's seal.

my experience is with the mc-1 drive, but your alpha should be the same.

 

[PETCH]

Thx Ziggy. I replaced the drive shaft seal last night in the upper housing. merc# 26-96503-1. It wasn't too bad of a job. I removed the adjacent water pipe, and used a pair of pliers to grab onto the edge of the aluminum part of the seal and got it out. Pressing the new seal in was a little nerve racking. You're a little off angle, so tough to press it in straight. But I tapped it in until it was flush. You're right, there were no other seals up there. The other seals shown in the diagram must be up in the top section.

thx!
Petch

 

[achris]

Hello,
New Boat Owner here: 1986 16' Peterborough Monza with a MCM140/Alpha one. The Alpha One, Gen one, is leaking oil from the Weep hole. So I am replacing the Shift Shaft seal and bushing, along with replacing the Impeller, gaskets, and both the top and base of the Impeller housing. I will pressure test unit before re-install.
My questions are in regards to the vertical Drive Shaft. With this older drive, I have the O-ring groove just below the spline. When I removed the lower unit, I found this O-ring had come off and was sitting up in the Upper Unit where the Drive Shaft seals are. I also found what appears to be another piece of a similar size O-ring up there. Must have been from prior owner.
Q: Do I install the shaft O-ring or not? I have read yes and no....

No need to put the 'O' ring on. More often than not it hangs up on the lower seal as the shaft goes in anyway, and holds the seal open. Completely defeating the purpose of the seal and the 'O' ring anyway. As Ziggy said, subsequent drive shafts don't even have the groove.

In the Upper unit, where the top of the verticle drive shaft slides into the Upper unit, there appears to be 2 seals. I'm trying to interpret the drawing in the link:
http://www.iboats.com/Mercruiser-St...8891364--**********.577619652--view_id.272967

The 2 seals seal different things, and are installed differently. The upper of the 2 seals on the outer diameter of the UPPER drive shaft and is installed from inside the top housing. It's about the first thing to go in when the housing is rebuilt.

The lower seal seals on the top of the lower drive shaft (the one that comes from the lower housing) just below the splines. That one is installed from the outside. I find it's easy to flick the old one out with a large screwdriver entering through the exhaust opening at the front of the housing. Installation is done by putting the seal in place on the housing and using a socket slightly larger than the seal to drive it in until the socket stops. That sets the seal in the right place, and level.

Q: What seals are used to seal the vertical drive shaft in the Upper Unit? Is there suppose to be an O-ring up in there in addition to the O-ring on the shaft?
part numbers 14 and 13 appear to have different ID's.......

The lower drive shaft is sealed by the lower of the 2 seals in the bottom of the top housing. Nothing else seals it. That why I replace that seal every other year.

Q: Can these seals be replaced from underneath?

Only the lower of the 2 seals. The top one seals on the upper drive shaft and is installed when the housing is completely disassembled.

HTH,

Chris......

 

[PETCH]

Thx Achris. The only other issue I had with this seal is when I was re-installing the lower unit. I must have bumped the edge of the seal with the tip of the drive shaft when raising it up. The spring in the seal popped out. The seal looked fine, so I got the spring back up into the seal groove. then was more careful when aligning the drive shaft. I've read where some people recommend assembling the lower into the upper unit out on a bench, doing it upside down for better visibility.....