Unsticking a stuck lower unit

[DennisG01]

A number of years ago I posted about a stuck lower unit: https://www.yamahaoutboardparts.com/...uck-lower-unit

No, I haven't gotten it off, yet Fortunately I boat in deep, clean water and the Yamaha impeller seems to be holding up very well - although I have tried a few times since. However, I brought the boat home with me this Winter (it's used/kept in Maine and I'm in PA) with the anticipation of getting back on this. Obviously, it's not going to be easier than it was a few years ago! However, I thought I'd start a thread up again and note my troubles along the way

I'll probably start up with this in the next few weeks or so. My plan, at this point, is to be the turtle, not the rabbit. I'll hang the engine upside down with most bolts removed and the remaining ones loose - probably add some wedges for good luck. Then dribble all kind of concoctions down the drive shaft towards the point where the shaft goes into the crank. Phosphoric acid... heavy duty vinegar... muriatic acid... PB Blaster... etc, etc.

I'm HOPING that one day I see that crack getting bigger! Last resort would be to cut a hole in the mid section and cut the crank and then repair the hole. Then I can at least get a slide hammer on the driveshaft and/or remove the power head and turn it upside down to get better access to the bottom of the crank.

To hang it upside down... my plan is to put two (in case one breaks) ratchet straps around the gear case, between the anti-vent plate and gear housing portion. Then tie a rope from one side of the strap to the other creating a loop to hang the engine. Any other ideas?

[99yam40]

is there any way to get the blade of an air hammer/chisel onto the drive shaft to vibrate the heck out of it while hanging and plenty of penetrating fluid on the shaft at the crank

[DennisG01]

is there any way to get the blade of an air hammer/chisel onto the drive shaft to vibrate the heck out of it while hanging and plenty of penetrating fluid on the shaft at the crank

Yes, that is definitely in the plans. I'll probably just cut-off a chisel that I don't use very much. I don't think I'll go TOO hard on it as I don't know what that would do the crank bearings/etc, though.

[ausnoelm]

Have you tried loosening the bolts, driving in wedges then starting the motor? That's probably the best method to remove it, failing that, a reciprocating saw through the join and cut the drive shaft.

[boscoe99]

I would loosen or remove all of the bolts. Then start and run the motor on the flush muffs. Hoping the crankshaft will get hot, expand and let go of it's grip on the drive shaft. While maybe pushing down on the lower unit to see if it moves at all.

[DennisG01]

Unfortunately, I did all that. Shifting a bunch of times, too, hoping the shock of gear changes would help.

[DennisG01]

a reciprocating saw through the join and cut the drive shaft.

Yeah, from above, that's my last resort!

[robert graham]

I would loosen or remove all of the bolts. Then start and run the motor on the flush muffs. Hoping the crankshaft will get hot, expand and let go of it's grip on the drive shaft. While maybe pushing down on the lower unit to see if it moves at all.

Seems like a pretty good idea to me!!

[zenoahphobic]

Yeah, from above, that's my last resort!

But then you will have a shorter piece of driveshaft stuck in the crank. Removal of powerhead would then be necessary so that the remaining driveshaft is demolished end on out of the crankshaft. I suppose you are prepared, if necessary to strip this engine and replace what is damaged along the way.

[ausnoelm]

Correct, if/when you cut the driveshaft, you have to remove the power head to get the splined end out, but, at least you can then work directly on it. Then the drive shaft has to be replaced, meaning gearcase work too. I personally would leave it all alone until it actually needs to be done, the water pump "might" last for years!

[DennisG01]

I may have mentioned it in my original post about this (the link in post #1)... maybe not... I didn't go back and re-read all of it But I do have a spare engine - with a bad cylinder and minus a few parts that I've used already. But it's a complet engine so I also have a good, spare lower unit. So IF I have to cut the shaft and IF I can then get the stub out I have another lower ready to go.

And, yes, cutting the driveshaft allows removal of the power head and makes working on the driveshaft easier. Note I said eas"ier", not "easy"

[ausnoelm]

It is reasonably easy to remove the cut driveshaft from the engine end, never had one that wouldn't come out, once you can access it, you can apply penetrating oil, use "some" heat, able to "tap" it back and forth with a hammer, all sorts of things are possible, I have seen a big washer welded to the end to use a slide hammer, not too sure on that one, but, it worked!

[DennisG01]

It is reasonably easy to remove the cut driveshaft from the engine end, never had one that wouldn't come out, once you can access it, you can apply penetrating oil, use "some" heat, able to "tap" it back and forth with a hammer, all sorts of things are possible, I have seen a big washer welded to the end to use a slide hammer, not too sure on that one, but, it worked!

Thanks, Aus!

[boscoe99]

Correct, if/when you cut the driveshaft, you have to remove the power head to get the splined end out, but, at least you can then work directly on it. Then the drive shaft has to be replaced, meaning gearcase work too. I personally would leave it all alone until it actually needs to be done, the water pump "might" last for years!

I had a 25 HP Mercury two stroke for several decades. Lots and lots of run time. I don''t recall ever having to change the water pump. The tell tale was always freely flowing water.

No over temperature warning device either. Only time it over heated was when I went through some shallow water and drug the bottom. Heard the motor starting to labour. Cleared the lower unit and the motor ran just fine. Ran fine when I sold it years later.

[Keithbaja]

When u get the motor turned upside down, drill a small hole above the drive shaft bushing (now below) and use the Lil red tube a start spraying at least in the morn and late afternoon. U can shoot up to get the bushing. Also, shoot some above the shiftshaft coupler. Which is seldom the problem. I highly recommend "AreoKroil" the stuff in the orange can. Makes all other penertrating oils, look like crap. Which it is, compared to what most of us call "Kro-Oil" if you called it "areokroil" to a part guy he might look at u strange.. Magic sauce. Miracle working stuff. Be very consistant and liberal with it. Good luck. U will get.. Trying to cut a driveshaft isn't the way to go..that's not needed unless u have a Super RARE case....