Driveshaft

[pass118]

So i pulled the lower unit on my 87 125 force and I looked at the top of the driveshaft and it was smooth almost looked like something broke off which would explain why my boat wont go into gear. My question is if something did break off how do I get it out, what would cause that to happen and can I find a replacement??? Thanks guys

 

[jerryjerry05]

Re: Driveshaft

Try a long magnet.If not you might need to remove the powerhead then drill and tap to pull out.Jerry

 

[pass118]

Re: Driveshaft

Yup as i looked at it this morning the shaft actually broke in half. Does anybody know what causes this to happen?

 

[MikDee]

Re: Driveshaft

Yup as i looked at it this morning the shaft actually broke in half. Does anybody know what causes this to happen?

Old Age! Like the rest of us,,,

If you want to save yourself some trouble, maybe you can get a threaded steel pipe coupling to fit, Or, a "steel socket weld coupling" in that size, (I know they make such a thing) I've welded them, it usually comes in a variety of sizes, 3/8" Iron pipe size (IPS) about 5/8" outer diameter (OD), Or, 1/2" IPS, 3/4" OD and have it welded. Or get a stainless steel one, whatever is required.

 

[Frank Acampora]

Re: Driveshaft

FIRST: Before you go crazy: Take a nice heavy piece of brass or aluminum to cushion the blows so you don't **** up the threads on the crankshaft. Then with a heavy hammer firmly rap the top of the crankshaft. It may take a good number of tries BUT if the splines have not jammed into the crank, the shaft will eventually drop out.

Next you need to determine why the shaft broke. Turn the stub by hand to see if the lower unit is locked up. Check the prop and cavitation plate for bends to see if a piece of wood was picked up and jammed it.

The shaft is really pricey so you need to see if you can pick up a whole lower unit or a junker. However, if you put a new or used shaft into your old lower unit, be very careful. It must be re-shimmed for proper pinion engagement.

 

[pass118]

Re: Driveshaft

Thanks for the reply Frank...yea the lower unit spins freely and the shaft split right in the middle so getting to the upper part that split (since the lower unit has been removed) is almost impossible. I've tried using a piece of hallow pipe and stuck it up around it and wigggled it around but no luck. Is there any way I can remove the mid-section or the upper and hit it down? Thanks

 

[Frank Acampora]

Re: Driveshaft

Perhaps I did not make myself clear in the first paragraph of my reply:

BEAT THE S++T OUT OF THE TOP OF THE CRANKSHAFT! The broken stub of the driveshaft will most likely fall out.

 

[captquest]

Re: Driveshaft

Perhaps I did not make myself clear in the first paragraph of my reply:

BEAT THE S++T OUT OF THE TOP OF THE CRANKSHAFT! The broken stub of the drive shaft will most likely fall out.

Hey Frank, I respect your knowledge and experience you have helped me in the past. But this reminds me of some thing I read in another post regarding some one trying to remove a flywheel. Have you ever heard of damaging the crank bearings by hitting to hard on the crankshaft? Recently I rebuilt my powerhead and found severely damaged bearings and the cause is still somewhat a mystery. Sry pass118, do not mean to hijack your thread, but this could be a concern.

 

[Frank Acampora]

Re: Driveshaft

I don't consider that a hijack--it is a logical question related to the thread and quite relavent.

In the first answer I recommended to "firmly rap" the top of the crank. It was either not read or mis-understood so I got a little more aggressive in my second reply. Also, I recommended using a brass or aluminum drift to take up some of the force and preserve the threads.

Brinnel is a rating of the surface hardness of a metal--usually steel--measured by pressing a hardened ball (bearing) or a rounded cone into it. Depth of penetration is brinnel number. Brinneling is the act of denting the races of a ball bearing or others by applying excessive impact forces. Bearings are "dead" hard and can withstand significant pounds per square inch forces. Indeed, they are amazing pieces of equipment. It is no accident that during WWII, the bearing factories in Germany were considered primary targets for bombing.

Think about the impact loads when an auto hits a pothole at 20 or 30 mph. The front suspension members may bend and even the spindle may bend, but the front wheel bearings will usually be ok.

BUT, Yes, it is possible to brinnel the bearing by using excessive force. However, the only bearing to worry about is the top ball bearing. The rest are rollers so the slight movement of the shaft won't affect them. And this top bearing is sized to take significant forces. Unless you do beat the living bejeesus out of the crank, it is unlikely that you will ruin the bearing. In all probability you will damage the nose of the crank first.

Firmly tapping the top of the crank is an approved method for removal of the flywheel so with a little respect and care, removing the driveshaft stub by this method poses very little danger to the bearing. It most likely won't come out with the first few raps so the hitting must be continued for some time. Last time I did it, I belted it a few times, walked away and did something else, then returned for another round.

BTW: that top bearing is a standard bearing used in the rear end of some Ford Vehicles. I have pressed them off the crank with a 60 ton (because 10 tons is not enough) press and not damaged them. This involves supporting the outer race and pressing the crank which puts the full load against the balls and races. Hitting the crank with a hammer is nowhere near the force needed to remove the bearing so again, the danger of damage is low.