TOPIC: To Grind Or Not To Grind...

The LU I put on my 68 merc 1000 does not have a slot for the O ring like my original.

should I grind a slit in it to accept the O ring?

If so what is the best way to do that?

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You definitely need an O-ring seal, since nothing else keeps the water out of the crankshaft splines. Otherwise, the splines will eventually rust-out, causing a very expensive repair (replacement of the crankshaft).

I'd find a grinding wheel of approx. the same width as the existing groove, mark the driveshaft to be grooved in the appropriate place (using the other driveshaft's groove as an example), and grind to suit. Just take it easy, go slow, and only remove as much material as needed.

Use the O-ring's fitment in the original driveshaft groove as an example.

HTH..........ed

So, were there 2 different designs? i'm to lazy to get the book in back room:)

I would use or make a depth gauge so you dont get it too deep. maybe a tooth pic and paper clip in hole epoxied, whatever? If you could find a round hand file to finish after using the grinder, sometimes these electric tools can get away from ya, even a dremel.

ps. just thought you might try a small pipe cutter to scrib over your line to help guide the grinder? splines might be too close though? All disclaimers apply

OR put a peice of hose cut about 3/4 in long and a real tight fit on the driveshaft put it high and when you put the lowerunit on it will adjust itself into a good sealing position. just a thought. lube the splines well and wipe the top so it does not pressurize the crank.

Be very careful ! If you are not a machinist, I'd be leery about an eyeball cutting of an o-ring groove.
If you cut too deep the o-ring is useless, and thus so is the shaft. If you cut to shallow, you'll cut the o-ring when you assemble, which makes it useless.
If the groove is not concentric with the shaft (meaning one side of groove deeper than the other) the o-ring is useless, because it will leak on the deep side, and cut on the shallow side
If the groove is too wide, the o-ring will wear really fast. because it will just flop around.
Make sure you have a set of calipers to measure the depth and width of the groove.

My guess for the two different designs of shafts are:
Yours has the o-ring on the shaft, and the other shaft has the o-ring groove in the housing ?
Since I have never worked on an outboard ...YET... I really can't comment on the shaft design.
But with my experience being a designer, that would be my guess ?
Good luck !!!!

I personally wouldn't mod the driveshaft, unless it could be removed from the lower unit and cut in a lathe. Trying to grind it freehand would be a bad move, I believe. If it ware mine, I'd go get a stick of "never seize" and put as much on it as possible. Slip the lower unit into position, then pull it back off. Re coat the splines again and do a final assembly. The stick (like a big chapstick) type never seize is better as the paste type may be easier to wash off over time.

A lot of good input here. I like Bruce's idea about the "never seez".

This is my spare lower unit to use while i'm rebuilding the original. As long as i can keep water out or minimal this summer It should be fine.

And maybe while it's off i'll put on a piece of hose like Dave recommended.

Once the other LU is ready and I swap them back I can determine if it warrants taking out the drive shaft and getting it lathed or keeping it as is.

If this were a wood working project I'd have no problem. But i don't trust my metal working skills to get it right.

I didn't wipe the grease off the top of the splines when i installed it. What kinds of problems can that cause if the crank is pressurized?

If you get a hydraulic lock on the driveshaft/crankshaft, it'll push the crankshaft upwards which causes strain on the upper and lower crank bearingw. Usually there will be a funny-sounding noise which accompanies the binding problem.

Grab hold of the flywheel and pull upwards. If you can feel a slight amount of vertical play in the flywheel, it's not "hydraulic'd".

However, without an O-ring in there, any excess grease is just gonna spill out around the driveshaft, so I think you're probably OK.

HTH..........ed

I kinda like Dave's idea. Simple, and a nice smooth straight cut will seal it good enough. I would not put any anything "sticky" (silicone, Never Seize) on it, as you never know what gonna stick up in there, and unseen, spoil the seal when you do the rebuild the old Leg. As it only a temporary while you rebuild the other, I see no problem.
Being a Machinist, I would not recommend cutting it with anything if not in a lathe. And for location, you would have to remove BOTH shafts, to measure the correct positioning of the cut to be made. THEN, doing the cut with a "spoon ground" tool bit using the original ORing groove for comparision, AND chamfer all sharp edges nice and smooth/rounded, to avoid and "stress risers".

A poor job could easily leave you a "unwanted", "2 piece" DS. And when something like that happens, thats when the splined piece always seems to get stuck in the C/S. Bitch to get it out. Been there..(working a friends motor). Simple hit a rock/log, and "damnit". And like Ed said, waterproof grease the splines, but go easy. AND always wipe excess off the top, the "Hydro Lock" thing. Can do more damage than thought. AND, also grease coat the whole shaft too. Can't hurt, especially if a steel shaft. (See pic). Hope this all works out good ferya!

Something I do on OMCs and did on my KG-9

I find O-rings that are tight on the shaft and as thick as you can get. Install 3 o4 4 with a bit of 3M glue to hold them in place about 2" apart.

They then work as a slinger and throw the water off before it gets to the block

TallTexan wrote:

Something I do on OMCs and did on my KG-9

I find O-rings that are tight on the shaft and as thick as you can get. Install 3 o4 4 with a bit of 3M glue to hold them in place about 2" apart.

They then work as a slinger and throw the water off before it gets to the block

Thats a great idea!

I tried a piece of rubber hose on the shaft but it wouldn't fit through the opening in the exhaust houseing. It wasn't a thick wall hose but it wouldnr fit through the opening. Ill see if i can find some o rings.

Then I'd simple take a ORing that fits tight, slide it on just past the splines, and slam it home. It will slip down when in the C/S and seal good enough. As not gonna be a permanent L/U, I wouldn't give it a second thought...

Makes sense. Now if I could just get reverse working I could start rebuilding the original lower unit.

I put on 3 of the smallest o rings i could find that would fit. They stretched and rolled on and were spaced an inch or so apart.

All 3 ripped as the shaft slid through the opening at the bottom of the middle unit.

So at least on my 68 1000 your not getting anything up in there that doesn't belong.

Thanks!