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Alpah 1 lower unit input shaft oring

L

lime4x4

Contributing Member
On a 1986 mercruiser alpha one

On a 1986 mercruiser alpha one lower unit. Is there suppose to be a o-ring on the input shaft just below the slines? When putting my unit back together i installed the o-ring on the shaft then i installed the lower unit back onto the upper unit. I had to pull the lower unit off to double check something and the shaft no longer had the o-ring on. It was in the upper unit past the seal. Is that o-ring needed?
 
"Loss of lubrication oil in up

"Loss of lubrication oil in upper OD and gear destruction, water in lower unit resulting in a new OD."
 
"The o-ring was originally the

"The o-ring was originally there to keep grease on the splines only. It turned out it was a weak link in the shaft and would often sheer at the oring groove.

There are two oil seals that keep the upper gear oil from comming down from the upper gear case.

It is also common that after installing the lower unit into the upper that the o-ring stays behind.

Get it out of there and if still in good shape reinstall it on the shaft otherwise replace it.

All alpha 1, II and I believe MR's do not have the oring or groove and the upper seal configuration did not change.

So to answer your question.......the oring can be left off the shaft but it is best to replace or reuse it. Also grease the splines!!"
 
"Sorry for sending you astray.

"Sorry for sending you astray.
blush.gif


Thanks for the explanation KG."
 
thanks guys. I was just wonder

thanks guys. I was just wondering. I saw the seals in the upper unit and just wondering what the purpose of the o-ring was for
 
When I pulled the lower on my

When I pulled the lower on my alpha 1 it had the groove but no o-ring so I put it back without one. Ok or not?
 
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