shaft nut torque spec?

[dheaton883]

Im rebuilding my lower unit on a 1970 chrysler 70hp motor model number 707ha. I have all the parts to put it back together but im in need of the torque spec for the shaft nut that holds the lower gears on. If anyone has any of the torque specs for any of the nuts on the lower end of this outboard, i would greatly appreciate them. thanks!

 

[dheaton883]

Re: shaft nut torque spec?

for anyone watching this link, I have called around to many outboard mechanics in the midwest region and the answer that i have gotten from everyone is to tighten the shaft nut snug and use lock tight. The internet doesnt have any free information on these late model motors with torque specs.

 

[Frank Acampora]

Re: shaft nut torque spec?

There is a torque specification which pre-loads the top and bottom bearings but I have forgotten it and my manual is in pieces. If you can find an Intertech manual on line you can probably find it there OR it MIGHT be in Clymers. I am going to go out on a limb ans say I THINK I remember a spec of 80 INCH pounds. Remember, that is with a new deformed nut so most of the torque goes toward spinning the nut onto the threads. At any rate, doupbe check the shaft to see that it is not binding at this value.

If you can't find the torque spec anywhere, then try just snugging the bearings to pre-load them, just like on a trailer wheel. Just be aware that too loose will change the pinion gear backlash and possibly destroy the gear-pak. Too tight wastes power and will overheat the bearings, also accelerating wear.

As far as the pinion nut, all manuals call for a new one each time the pinion is removed. HOWEVER: It is a deformed thread nut that locks on the threads. You can "stake" three sides with a punch to renew the deformation or you can squeeze the nut in a vise to make it slightly oval. Both methods will satisfactorily lock the nut on the shaft.

 

[dheaton883]

Re: shaft nut torque spec?

Thanks Frank. I ended up finding a new nut at the local boat store. They let me dig through a box of never used parts that they had in the back room. I installed the nut with lock tight. I turned the nut on little by little turning the shaft after evey time i tighned the nut making sure the bearings arent stressed and also not too loose. I came to the conclusion when there was a tiny pressure on the bearings but also the shaft spins freely. I have the upper lower unit at the machine shop getting the seal under the water pump pushed in. I have the lower lower unit put together and ready to be assembled. Ill post how this goes when im done this weekend. cant hook the water up to it because of a snow storm this weekend tho.