Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

[Daibheid]

Hi Guys,<br /><br />I've got the Lower Unit Blues but baaaad! I've read most if not all of the posts here on this popular topic before I attempted to drop and open the LU on my newly acquired '81/2/3 70 HP 3 Cyl Mariner/Mercury S/N is 6074129. It hasn't had an <br />impeller in 3-4 years and reverse ain't engaging hinting at the need for a new clutch - at least! As I'm away this weekend I hoped to ID the problem and get the parts on order.<br /><br />But I can't get the LU to drop. Perhaps you guys can spot something I'm missing or suggest a remedy.<br /><br />I drained the oil to see how it looked. Not bad condition but I didn't think there was a lot of it - certainly less than a pint. Can anyone tell me how much I should have seen?<br />There was no water but the magnet on the fill/drain plug was fairly covered with fine bits of metal. Although I've seen similar on car engine plugs it made me anxious to get it open and inspect the 'guts'.<br /><br />I took the prop off and loosened the threaded ring as it seemd easier to do it while the LU was on the engine. After carefully opening the four nuts that hold the LU in place, I got the hidden under the anode one, and with foward gear engaged, a gentle tap of copper mallet parted the LU but it only dropped about 1/8th". Working it up and down made no difference giving only a clang sound from within.<br /><br />I sprayed penetrating oil and WD40 liberally into the area to no avail. I then hit on the idea of putting two 1/8th" thick pieces of hardwood above the two nuts at either side at the front of the LU. By opening the nuts against these I was able to exert a lot of downward thrust on those two studs each side of the drive shaft - again to no avail. I then backed off and went through it from scratch to see if I'd <br />missed anything. I verified I could move the shift shaft up at the top of the engine which leads me toward the conclusion the drive shaft has frozen or corroded on the splines with the engine. I can't detect any end play in <br />the crankshaft even with the LU back up fully so can't determine whehter this is no indeed zero play or a stuck shaft.<br /><br />I then set my pusher blocks in place again and wound up the tension hard and tried shocking the LU with my copper friend. I even tried striking the centre of the crankshaft with a punch hoping the combination of shock and tension might free it. Nope. Anyone able to tell me how robust that drive shaft and bearing assembly is in terms of applying tension? I'd hate to pull the lower pinion/bearing assembly up through the LU.<br /><br />Trying a bit of lateral thinking I reasoned that if I took the prop shaft out, I could undo the pinion retaining nut on the bottom of the drive shaft to allow the LU come down and give me a chance of getting at the suspect siezed shaft joint. I suspect I'd total the water pump doing this though but I couldn't get the prop bearing carrier to move (after removing the ring and lock washer) but really didn't try too hard as it looked fragile so would appreciate any advice on how best to get this puppy out. I'm planning on a scissors jack on hte nd of the prop shaft with a webbibg strap through the bearing carrier.<br /><br />I read someone else had a horror story with a similar stuborn LU and I learned a lot from that series but I'd really appreciate any ideas on where to go from here. <br />A key question is how best to get penetrant at the shaft joint if you agree with my diagnosis?<br /><br />FYI I tried remoing the LU in F and N and R (sort of. I can't remove and/or invert the engine to fill it with diesel/pentrant although I <br />briefly considered driving it up the road with the skeg dragging on the deck to see if that 'd free it!<br /><br />It's been a long night.......<br /><br />Regards,<br />Dave

 

[Chris1956]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Dabheid, I cannot say I am an expert on your particular motor, but it does sound like a stuck driveshaft. If you pull the pinon nut, the waterpump will still not allow the drive shaft to pass up the lower unit. I have heard of folks attaching the powerhead to a tree with a chain, and the lower unit to a tree with a chain and "Come along", and using force to seperate the units. You may end up doing this. <br /><br />Alternatively, how about if you hang the motor upside down, 2" above the soft ground and spray good penetrating oil into the 1/8' gap and hopefully onto the drive shaft. Gravity should put the oil into the correct place, and may eventually cause the unit to seperate, without damage.

 

[quantumleap]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Use shims in the crack that you've opened and smack the he// out of it! also try using the biggest rubber mallet you can find to strike the lower unit top. Put a towel on top to keep from scratching it. It will eventually come off.

 

[emckelvy]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Yes, very thin "machinist wedges" are just about the only answer, other than cutting the driveshaft, which isn't too desireable!!<br /><br />Don't beat on the top of the crank too much, it isn't good for the bearings. Of course, you're likely to find that the crank splines are stripped out, in which case it won't really matter.<br /><br />Sometimes it may help to turn the motor upside down and try to spray penetrating fluid into the split between the gearcase and center section; hopefully it'll run down the driveshaft and get some oil up into the splines.<br /><br />HTH and Good Luck.......ed

 

[andrewkafp]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Most posts on here succeed by "Belting" it off using a mallet, wedges and wood blocks. If it is in fact later than 1980 it has a stainless steel drivesahft and should resist corrosion. I would not bother with removing anything other than the nuts found on the L/U maiking sure you got them all.

 

[Daibheid]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Thanks to you all for your suggestions -especially Unicorn letting me know it's probably a stainless shaft. I'm persevering with applying pressure and whacking the LU from the side and downward via the anticav plate. I also tried pushing down the LU via my two nuts on studs at the front only leaving the annode end in contact with the leg. The idea was to put a little curve in the shaft while I turned the engine by hand with the fly-wheel. The engine is very difficult to turn with the LU stretched downward pretty well confirming the shaft and crank-shaft are seized together.<br /><br />In fact it feels so solid that I really felt I had to find some way to get some WD40 on to the drive shaft/engine joint or it will never move with brute force alone. I found that small gap at the LU wouldn't allow me access the drive shaft with a spray because there seems to be a downward mating protrusion into it from the leg and I can't separate it enough to get a nozzle up past that. Plus I think the waterpump would be in the way. I was seriously thinking it would make sense to drill a small hole through the leg toward the top to spray into it. I could tap this and block it with a bolt or even epoxy filler.<br /><br />Before I'd resort to that I started looking for other bolts that might allow access or could be drilled on through the leg to spray into the upper shaft area. I eventually found that at least one of the bolts holding the starboard lower isolation bushings is in fact a through hole. (The other one sheared so that's a stainless bolt in soft alloy headache to deal with later).<br /><br />So last night I emptied a can of WD40 upward via a bent nozzle through this hole which is almost exactly in line with the shaft. I'm hoping a splash or two at least hit the splined joint about a foot above and will keep at it over the next few days.<br /><br />I hope at least someone else might benefit sometime from knowing you can get some sort of shaft access on this engine at least and that a hole into the leg in this area would be unlikely to hit any other passageways.<br /><br />My manual is on the way but could anyone tell me the specific LU oil quantity for this engine?<br /><br />I'll let you all know if I get it dropped!<br /><br />Thaks again <br />Dave

 

[Chris1956]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Daibheid, The lower unit on my inline six uses about 3/4 of a liter of EP-90 gear oil.<br /><br />On the matter of seperating the housings. I would consider hanging the motor upside down and spraying the penetrating oil into the i/8" gap between them. The exhaust housing is directly behind the driveshaft, and if you spray liberly in front of it, some is bound to get on the driveshaft, and gravity will send to the powerhead-to-driveshaft joint. I do not know of a way to get the oil onto the splines, while the motor is upright, since the driveshaft fits into the end of the crankshaft!

 

[quantumleap]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

If you drive wedges in the crack it will come off. That is the easiest way to get it to break free. Place hardwood or metal wedges on both sides and have you and a friend similtaneously wack both sides with a heavy sledge type hammer and it will drop. The evenly applied force to both sides will work. Don't be timid. Wack the crap out of it.

 

[andrewkafp]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Dead right Quantum.. Diabheid, go through the posts and this wedge and whack method is the most successfull. It WILL come off, I've read many posts on here where the shotgun had to be returned to the gun rack and the L/U came off.<br />When you put it back on, make sure you clean and grease the splines .. for the next time <br />BTW are you SURE you got all the bolts inc the one under the tab ?

 

[merc_500]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Originally posted by Chris1956:<br />I have heard of folks attaching the powerhead to a tree with a chain, and the lower unit to a tree with a chain and "Come along", and using force to seperate the units. You may end up doing this.

hehe i had to do that to remove the flywheel from my old dirbike, tie the motor to a tree, flywheel to the car........

 

[Daibheid]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Success! Thanks to all of you for your helpful advice and encouragement after 5 nights of battering banging, wedging, jacking, etc it's off. The encouragement to really whack it was essential.<br /><br />The shaft is indeed stainless and showed signs of being seized. The little sprung insert shaft for pushing out endplay was rusted in place causing most of the grief by contaminating the shaft splines. <br /><br />I think the killer weapon is indeed the wedge with shims approach although I enhanced it by removing the water inlet screens and putting a bar through therelinked to two side plates connected by another bar below the skeg. Hammering on this lower bar really sent a nice shock right down the line of the drive shaft.<br /><br />I've sorted the impeller and reverse seems to engage OK when the LU is down although it's difficult to really tell as it ratchets one way anyhow. I was willing to strip the gearbox but couldn't get the prop shaft bearing carrier to move. I used steel cable around two of the supports and a jack on the prop shaft nut with a LOT of pressure applied before I chickened out. Actually I broke the cable although it was only 1/16th to 1/8th". <br /><br />So I decided to mount it all up again and see if the reverse shift issue was resolved.<br /><br />I can't get the damn thing to go back up now as the shifter seems unwilling to align and slide home no matter whether I do it in F,N or R. I've even disconnected the shift cable to allow it float while I push the LU back up. I set it up so I could lever the LU up while I rotated the flywheel and jiggled the shifter via the lower leg as it comes out of the LU. As there are only a few coarse splines it seems almost impossible to be a spline out so is there anything the cam or anything else can do to misalign the splines? Reading all similar posts I think I saw Johnsons can have the shift cam rotate fully and reset.<br /><br /> Suggestions appreciated - you guys got me this far!<br /><br />Thanks again.<br />Dave

 

[andrewkafp]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

You need to have the L/U in the same gear as the upper shift shaft. There is a post that I will find that explains very well the tecnique for re-assembly.. So far I think you have had THE LUCK OF THE IRISH... getting if off <br />2 things you need to remember.. Grease the splines (not too much though) and remove that L/U <br />and the prop every second season to prevent seizing. You can do the impeller at the same time.<br />Did you replace the plastic driveshaft seals and the spring ? They are low cost and worth replacing.<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=29;t=010967;p=1#000011

 

[Daibheid]

Re: Lower Unit No LongerHanging Up - Merc/Mariner 70 Hp 3cyl

Thanks Unicorn - I had it back on by the time I saw your helpful post. I think a great deal of my difficulty in getting it back up was greasing the splines. I found it would go up with some tappping and then help from the securing nuts. with the benefit of your post and a freshly acquired Clymer I guess it was 'hydraulicing'. I'll use a thin layer of oil next time it's off which shouldn't be long as when back in place it still won't engage reverse even with the control cable removed and the shift slider at the top of the engine pushed right to the back of the slot. the prop just ratchets in both directions.<br /><br />It seemed securely in reverse when the LU was off the engine and also when initially just mated to the engine and shift shaft when the prop could turn the engine in reverse. <br /><br />There were no seals up at the engine end of the shaft. It looks like there should have been something. Is this the plastic sleeve you were talking about Unicorn?<br /><br />Thaks again to you all for your help.<br /><br />Dave