Mercury lower unit
 

I need a new lower unit for my 1979 70 hp Mercury outboard (long shaft).
I've found one, but it's for a short shaft). Aside from the length of the
drive shaft, is there any difference in the two?

Thanks,

Tom

Yes the case has to be extended the same amount as the shaft.There are case
extension available.
"Tom Creech" wrote in message
...
I need a new lower unit for my 1979 70 hp Mercury outboard (long shaft).
I've found one, but it's for a short shaft). Aside from the length of the
drive shaft, is there any difference in the two?

Thanks,

Tom

There should be no difference but, unfortunately, the gear case must be
taken completely apart to change the drive shaft. I ran into that last year
and to take both the old and new apart, change drive shafts, etc. made a
"deal" cost prohibitive. If you can find someone who will furnish you a
guaranteed (long shaft) one at a price you can live with, then go for it.
For my 200 merc, I got one for $450 that continued to leak, eventually
swapped it for a $1000 which has worked good and I trust the guy I got it
from!
LD

"Tom Creech" wrote in message
...
I need a new lower unit for my 1979 70 hp Mercury outboard (long shaft).
I've found one, but it's for a short shaft). Aside from the length of the
drive shaft, is there any difference in the two?

Thanks,

Tom

Now I'm not so sure that it's a short shaft.
Part # crosses to short shaft assembly, but seller says that the exposed
shaft (sticking out of lower unit) is 21".
That would be a long (20") shaft, right?
I'm thinking that someone rebuilt this for a long shaft..
Any thoughts?

Thanks again,

Tom
"Tom Creech" wrote in message
...
I need a new lower unit for my 1979 70 hp Mercury outboard (long shaft).
I've found one, but it's for a short shaft). Aside from the length of the
drive shaft, is there any difference in the two?

Thanks,

Tom

Sorry, I don't remember the exact dimensions but I seem to recall a "20" and
a "25". I believe the actual dimensions referred to are from the underside
of the transom clamp (that would rest on top of the transom) down to the c/l
of the prop shaft. The easiest way to check against another otherwise
identical motor though, is to measure the mid section--from the bottom of
the powerhead to the top of the "foot".
LD

"Tom Creech" wrote in message
...
Now I'm not so sure that it's a short shaft.
Part # crosses to short shaft assembly, but seller says that the exposed
shaft (sticking out of lower unit) is 21".
That would be a long (20") shaft, right?
I'm thinking that someone rebuilt this for a long shaft..
Any thoughts?

Thanks again,

Tom
"Tom Creech" wrote in message
...
I need a new lower unit for my 1979 70 hp Mercury outboard (long shaft).
I've found one, but it's for a short shaft). Aside from the length of
the
drive shaft, is there any difference in the two?

Thanks,

Tom