Shortening a driveshaft

[Tom Smyth]

Need helpplease onthis. Have a 1970 1350 merc that i am changing over from Long shaft to short shaft.

Ready to send the Ddriveshaft to have it cut and resplined but wold GREATLY appreciate help in figuring out how much to chop off.

Measured the difference inthe two driveshaft housings.
Long shaft housing measures 20.250 inches .

short mid measures 15.875 inches.

These measurements do not include the top adapter plate and are measured to the flange where the lower unit mounts.

Difference is 4.375 inches.


I had always heard that there was only 4 inches difference between a LS and SS motor.

Can anyone confirm this ( 4.375) is the amount to chop off??


Thanks

Smytty

[T-REX]

I've alwayz cut off 5".....Tha differnce between a 20" and a 15" iz 5" down yher...I juss measured my drive shaft outta my 15" mota, aginst a new, outta tha box 20" shaft, and it iz exzakly 5"!!!....I muss be doin sumpth'in wrong:rolleyes:

[Bruster]

I've alwayz cut off 5".....Tha differnce between a 20" and a 15" iz 5" down yher...I juss measured my drive shaft outta my 15" mota, aginst a new, outta tha box 20" shaft, and it iz exzakly 5"!!!....I muss be doin sumpth'in wrong:rolleyes:

Rex-
Wack an inline 5" and you'll be an inch short. But you're used to hearing that 'eh?:eek:

[Mark75H]

The difference is probably in spline engagement in the crank. Normally there is a lot of engagement. If you cut off 5 and the actual measurement is closer to 4.5 you are probably only loosing excessive spline engagement.

[Tom Smyth]

Measured my 1350 long shaft drive shaft against my 76 850 XS shortie. 4.5 inches difference....

But the lower end geometries arent exactly the same...

[crazy horse]

Tom, I have both shaft designs in a short case so I could measure them for ya? I don't have a loose driveshaft for a short inline but I do have a couple of XS cases and some ssm's layin around.:D

[Bruster]

I measured 2 driveshafts and 4-3/8 is pretty close maybe 4-7/16ths. Kind of hard to be exact with one shaft is original sealed package. I wacked one 5" and all it would do is nothing, but it was easy to put on.:D

[Tom Smyth]

So sounds like if i went 4.5 inches i should be fine ..

CH - so haow many SSM you got laying around that you want to part with ??:)

Smytty

[baldad45]

I have a new 1500XS driveshaft and it is 26 1/4'' total overall .

[T-REX]

OH ya'll talk'in inline'z!!!!!!!...........Sorry, I know more about what causes womenz mood swangz den inline 6'z.........I wuz talk'in v-6'z, so disregauard what I said, I wuz hilousinat'n agin!!

[fijjity]

I just had 2 done:D

[camaro7081]

how much to have shaft cut down ? and who can do this ? sounds much easier then having some shop change the shaft .