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Author Topic:   1987 Mercury Outboard: Removing Gearcase

Brys13s posted 12-31-2005 05:57 PM ET (US)
I'm having trouble removing the lower unit from my 1987 35hp Mercury. I can only get it to separate about 6-mm from the midsection. I removed the four nuts that secure it to the midsection and this thing just won't budge. It seems that the driveshaft splines might be rusted together, but I'm not positve about that. Any suggestions?
jechura posted 12-31-2005 06:28 PM ET (US)
Did you disconnect the shift linkage?
Brys13s posted 12-31-2005 07:01 PM ET (US)
The motor is off the boat so yes the shift linkage has been disconneced where the cables go into the motor at the powerhead.The lower unit is in foreward gear like the service manual suggests for removing the lower unit{but I think that is just so you can tilt the motor upward assuming that it is mounted on the transom of a boat.}Where should the shift linkage be disconneced?
DillonBW posted 12-31-2005 08:46 PM ET (US)
If it is like my Johnson, you will need to disconnect a rod and lever inside under the carbs somewhere.
I had the same issue with my motor until some good fellows here pointed out this detail.
When you do get it of, make sure you get everythingset right or you may find you only have one gear! All ahead or all astern!
Best of luck.
Si

jechura posted 12-31-2005 08:57 PM ET (US)
Not sure, but the disconnect may be between the water intake screens. If you see a double nut, that's it.
lorin posted 12-31-2005 08:58 PM ET (US)
When jechura asked if you disconnected the shift linkage, he actually meant the shift rod, which has nothing to do with the shift cables. As DillonBW said, some shift rods can be disconnected under the carbs. However this is not true on all motors. On different motors, the shift rod is disconnected in various places between the powerhead and the somewhere on the gearcase. You need to find out where the shift rod disconnects on this specific motor. If you cant find it, a service manual would tell you.
sosmerc posted 12-31-2005 10:16 PM ET (US)
Unfortunately, there is nothing more to disconnect.....you most likely have a stuck driveshaft.
It is common for the driveshaft to "weld" itself inside the crankshaft. Merc recommends removing the lower unit on an annual basis..to service the water pump, but also to lube the splines on the driveshaft and the shift-shaft and the studs on the lower unit.
You are going to have to use wedges between the lower unit and the driveshaft housing to try and pry the lower unit off. If you have no success.....the next step is to use a hole-saw to drill a hole through the driveshaft housing up near the area where the driveshaft enters the crankshaft...then cut the driveshaft with a saws-all or a cutting torch. The driveshaft can be re-welded together after you pull the powerhead and remove the stub shaft from the crankshaft...if you can. (that's another battle).
Sorry, but lack of proper service is the cause for all this grief. Anything can be fixed......but the cost of this repair may be beyond "reasonable" based on the age of the engine.
lorin posted 01-01-2006 02:32 AM ET (US)
I'm not real familiar with this motor, but on a few other motors (OMC's) I've used the method of hanging the motor upside down and squirting wd40 onto the drive shaft to help release the stuck shaft. I did it 3 or 4 times and it worked every time although once I remember it took a couple of weeks. I'm wondering if this possible on this motor, even if you'd have to suirt the wd40 through the small opening between the gearcase and exhaust housing to reach the drive shaft?
Brys13s posted 01-01-2006 05:31 AM ET (US)
Unfortunatly,I don't have any pictures,but this is what I,ve done so far.I put some metal shims in beetween the top of the nuts that hold the lower unit on and the mid section.So when I loosen the nuts it puts pressure down on the studs that go into the lower unit and pushes it down.I don't want to put too much pressure on it because something might break.As far as getting some penetrating oil on the driveshaft,there's just not enough room to get in there,but I'm still gonna try.I'm hoping that by keeping pressure on it over time{like lorin said}that it might free up eventually.If not,mabye a new motor for next season.
Clark Roberts posted 01-01-2006 07:27 AM ET (US)
Brys, there is a hidden bolt underneath the trim tab (the little fin at rear of lower unit). Remove the fin by taking out the bolt on top of it and you will find the hidden recessed hex bolt. Remove this bolt and unit should come off. There is a splined connection to shift shaft just like the drive shaft and it just slips off...NO disconnect required. Be sure to leave as is so it will go back on properly. Good luck...and happy Whalin'... Clark... Spruce Creek Navy
Brys13s posted 01-01-2006 09:17 AM ET (US)
I removed the trim tab, the nut that is underneath it, the other nut on the bottom just about in the middle that is not hidden, and the two nuts on top. I wish I had forgotten about the one under the tab. Thanks anyway. I think sosmerc is right because to my knowledge the lower unit has not been off the engine for about6-7 years.
Brys13s posted 01-01-2006 05:58 PM ET (US)
I think I'll try a combination of what lorin and sosmerc said.Instead of a hole saw,mabye a 7/16"-3/4"hole in the mid section,{so it can be tapped and plugged with a ss bolt later}so I can access the driveshaft with a flashlight and penetrating oil while the engine is upside down.
lorin posted 01-01-2006 07:47 PM ET (US)
I suggest looking at a parts catalog before drilling. I'm not very familiar with Mercs, but I know on older 30hp OMC's, as the drive shaft exits the water pump it immediately enters a small plastic tube (I think it's called the water pump housing spacer). Then it passes into the aluminum exhaust housing. So on these motors, it would be easier to drill through the midsection and the plastic spacer (a reallly cheap part) than it would be to drill through the midsection and then the aluminum exhaust housing. Mercs might be similar but I dont know. If you do it, try to spray a few times a day, and put the motor in gear so you can turn the drive shaft around by spinning the prop a little.
WHALER27CC posted 01-01-2006 10:41 PM ET (US)
Sos merc IS 100 PERCENT CORRECT!! His assesment is right on the nose!!!
I know this because I went through the EXACT same thing with my 45hp Merc, I even tried hanging it upside down for 6 months by the lower unit while adding lubricating oil occasionally and re-jamming in metal shims to try to "unweld" it....No go. In the end I had to get rid of the motor because I wasnt willing to go through the added expense of cutting the into the driveshaft housing and cutting it as Sosmerc pointed out. This motor has a spline shaft that sits into tightly into a seat on the upper end. If the lower unit isnt removed every 2 years MINIMUM on this motor, it will freeze in place and basically it becomes a matter of time before the impeller will give out and overheat the engine. Unfortunately this motor is or will be junk when the impeller goes. In my situation I wasnt willing to risk it for obvious safety reasons. Sorry for the bad news.
jimh posted 01-02-2006 11:33 AM ET (US)
I am not a Mercury expert, but on my older Mercury the shift shaft was a splined rotating shaft and it just pulled out of the midsection along with the driveshaft; there was no need to disconnect anything in the engine cowling area. The OMC motors all seem to have a shift shaft that moves up and down (as opposed to rotating); these shafts need to be disconnected from a linkage in the cowling before the gearcase can be dropped off.
Brys13s posted 01-02-2006 07:18 PM ET (US)
I'm still gonna try to get this thing off only because right now I have time and belive it or not,the rest of the motor is in pretty good shape.It's clean and runs great.However,I know that it might not come off and if it dosen't,I'll junk it.[don't want to be out on the ocean and have the water pump go and blow the engine although I do have a 7.5 johnson kicker on the back.]Itsa challange and a nice project to help the winter go by faster.I'm working on it during the day and checking out new outboards on the net at night.I do like working on engines,but I also like buying new toys.We,ll see what happens.P.S. Happy new year to everyone.
Clark Roberts posted 01-03-2006 08:21 AM ET (US)
Consider making a hole(approx 1 1/2" with hole saw)through the mid section, at a location approx 2-3 inches below power head to expose the drive shaft. Now, apply as much heat as possible with torch and this may loosen the seized spline. If successful the hole can easily be covered/plugged. I have done this and it can work! Hang engine upside down and have at it... Keep a fire extinguisher handy... Clark...SCN
Brys13s posted 01-03-2006 07:18 PM ET (US)
Clark,what did you do to plug up the 1.5"hole?I'm thinking mabye tig weld a plate over it.By the way,do you know if the mid section is aluminum,magnesium or something else? I hope it's not magnesium for safety reasons.
Clark Roberts posted 01-03-2006 07:45 PM ET (US)
Mid-section is aluminum. I covered the hole with a plate via sheet metal screws. Put as much heat on the shaft as you can...also dousing with cold water may help break the bond. Clark... SCN
cbgann posted 01-03-2006 07:57 PM ET (US)
Before cutting the big hole, you might try a small hole flip the engine and use PB Blaster instead of WD40. Good Luck
Brys13s posted 01-03-2006 08:32 PM ET (US)
Yeah,I still might try that as I mentioned on my 01/01/06 thread,so that it can be tapped and plugged with a ss fastener.I'll start small and go bigger if I have to.I would not use WD-40 for this application.PB Blaster,Liquid Wrench,NAPA Penetrating oil or something simmilar would be the choices.I think WD-40 is good stuff if it is used for what it was made for,but that's a whole different topic.

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Author	Topic: 1987 Mercury Outboard: Removing Gearcase
Brys13s	posted 12-31-2005 05:57 PM ET (US) I'm having trouble removing the lower unit from my 1987 35hp Mercury. I can only get it to separate about 6-mm from the midsection. I removed the four nuts that secure it to the midsection and this thing just won't budge. It seems that the driveshaft splines might be rusted together, but I'm not positve about that. Any suggestions?
jechura	posted 12-31-2005 06:28 PM ET (US) Did you disconnect the shift linkage?
Brys13s	posted 12-31-2005 07:01 PM ET (US) The motor is off the boat so yes the shift linkage has been disconneced where the cables go into the motor at the powerhead.The lower unit is in foreward gear like the service manual suggests for removing the lower unit{but I think that is just so you can tilt the motor upward assuming that it is mounted on the transom of a boat.}Where should the shift linkage be disconneced?
DillonBW	posted 12-31-2005 08:46 PM ET (US) If it is like my Johnson, you will need to disconnect a rod and lever inside under the carbs somewhere. I had the same issue with my motor until some good fellows here pointed out this detail. When you do get it of, make sure you get everythingset right or you may find you only have one gear! All ahead or all astern! Best of luck. Si
jechura	posted 12-31-2005 08:57 PM ET (US) Not sure, but the disconnect may be between the water intake screens. If you see a double nut, that's it.
lorin	posted 12-31-2005 08:58 PM ET (US) When jechura asked if you disconnected the shift linkage, he actually meant the shift rod, which has nothing to do with the shift cables. As DillonBW said, some shift rods can be disconnected under the carbs. However this is not true on all motors. On different motors, the shift rod is disconnected in various places between the powerhead and the somewhere on the gearcase. You need to find out where the shift rod disconnects on this specific motor. If you cant find it, a service manual would tell you.
sosmerc	posted 12-31-2005 10:16 PM ET (US) Unfortunately, there is nothing more to disconnect.....you most likely have a stuck driveshaft. It is common for the driveshaft to "weld" itself inside the crankshaft. Merc recommends removing the lower unit on an annual basis..to service the water pump, but also to lube the splines on the driveshaft and the shift-shaft and the studs on the lower unit. You are going to have to use wedges between the lower unit and the driveshaft housing to try and pry the lower unit off. If you have no success.....the next step is to use a hole-saw to drill a hole through the driveshaft housing up near the area where the driveshaft enters the crankshaft...then cut the driveshaft with a saws-all or a cutting torch. The driveshaft can be re-welded together after you pull the powerhead and remove the stub shaft from the crankshaft...if you can. (that's another battle). Sorry, but lack of proper service is the cause for all this grief. Anything can be fixed......but the cost of this repair may be beyond "reasonable" based on the age of the engine.
lorin	posted 01-01-2006 02:32 AM ET (US) I'm not real familiar with this motor, but on a few other motors (OMC's) I've used the method of hanging the motor upside down and squirting wd40 onto the drive shaft to help release the stuck shaft. I did it 3 or 4 times and it worked every time although once I remember it took a couple of weeks. I'm wondering if this possible on this motor, even if you'd have to suirt the wd40 through the small opening between the gearcase and exhaust housing to reach the drive shaft?
Brys13s	posted 01-01-2006 05:31 AM ET (US) Unfortunatly,I don't have any pictures,but this is what I,ve done so far.I put some metal shims in beetween the top of the nuts that hold the lower unit on and the mid section.So when I loosen the nuts it puts pressure down on the studs that go into the lower unit and pushes it down.I don't want to put too much pressure on it because something might break.As far as getting some penetrating oil on the driveshaft,there's just not enough room to get in there,but I'm still gonna try.I'm hoping that by keeping pressure on it over time{like lorin said}that it might free up eventually.If not,mabye a new motor for next season.
Clark Roberts	posted 01-01-2006 07:27 AM ET (US) Brys, there is a hidden bolt underneath the trim tab (the little fin at rear of lower unit). Remove the fin by taking out the bolt on top of it and you will find the hidden recessed hex bolt. Remove this bolt and unit should come off. There is a splined connection to shift shaft just like the drive shaft and it just slips off...NO disconnect required. Be sure to leave as is so it will go back on properly. Good luck...and happy Whalin'... Clark... Spruce Creek Navy
Brys13s	posted 01-01-2006 09:17 AM ET (US) I removed the trim tab, the nut that is underneath it, the other nut on the bottom just about in the middle that is not hidden, and the two nuts on top. I wish I had forgotten about the one under the tab. Thanks anyway. I think sosmerc is right because to my knowledge the lower unit has not been off the engine for about6-7 years.
Brys13s	posted 01-01-2006 05:58 PM ET (US) I think I'll try a combination of what lorin and sosmerc said.Instead of a hole saw,mabye a 7/16"-3/4"hole in the mid section,{so it can be tapped and plugged with a ss bolt later}so I can access the driveshaft with a flashlight and penetrating oil while the engine is upside down.
lorin	posted 01-01-2006 07:47 PM ET (US) I suggest looking at a parts catalog before drilling. I'm not very familiar with Mercs, but I know on older 30hp OMC's, as the drive shaft exits the water pump it immediately enters a small plastic tube (I think it's called the water pump housing spacer). Then it passes into the aluminum exhaust housing. So on these motors, it would be easier to drill through the midsection and the plastic spacer (a reallly cheap part) than it would be to drill through the midsection and then the aluminum exhaust housing. Mercs might be similar but I dont know. If you do it, try to spray a few times a day, and put the motor in gear so you can turn the drive shaft around by spinning the prop a little.
WHALER27CC	posted 01-01-2006 10:41 PM ET (US) Sos merc IS 100 PERCENT CORRECT!! His assesment is right on the nose!!! I know this because I went through the EXACT same thing with my 45hp Merc, I even tried hanging it upside down for 6 months by the lower unit while adding lubricating oil occasionally and re-jamming in metal shims to try to "unweld" it....No go. In the end I had to get rid of the motor because I wasnt willing to go through the added expense of cutting the into the driveshaft housing and cutting it as Sosmerc pointed out. This motor has a spline shaft that sits into tightly into a seat on the upper end. If the lower unit isnt removed every 2 years MINIMUM on this motor, it will freeze in place and basically it becomes a matter of time before the impeller will give out and overheat the engine. Unfortunately this motor is or will be junk when the impeller goes. In my situation I wasnt willing to risk it for obvious safety reasons. Sorry for the bad news.
jimh	posted 01-02-2006 11:33 AM ET (US) I am not a Mercury expert, but on my older Mercury the shift shaft was a splined rotating shaft and it just pulled out of the midsection along with the driveshaft; there was no need to disconnect anything in the engine cowling area. The OMC motors all seem to have a shift shaft that moves up and down (as opposed to rotating); these shafts need to be disconnected from a linkage in the cowling before the gearcase can be dropped off.
Brys13s	posted 01-02-2006 07:18 PM ET (US) I'm still gonna try to get this thing off only because right now I have time and belive it or not,the rest of the motor is in pretty good shape.It's clean and runs great.However,I know that it might not come off and if it dosen't,I'll junk it.[don't want to be out on the ocean and have the water pump go and blow the engine although I do have a 7.5 johnson kicker on the back.]Itsa challange and a nice project to help the winter go by faster.I'm working on it during the day and checking out new outboards on the net at night.I do like working on engines,but I also like buying new toys.We,ll see what happens.P.S. Happy new year to everyone.
Clark Roberts	posted 01-03-2006 08:21 AM ET (US) Consider making a hole(approx 1 1/2" with hole saw)through the mid section, at a location approx 2-3 inches below power head to expose the drive shaft. Now, apply as much heat as possible with torch and this may loosen the seized spline. If successful the hole can easily be covered/plugged. I have done this and it can work! Hang engine upside down and have at it... Keep a fire extinguisher handy... Clark...SCN
Brys13s	posted 01-03-2006 07:18 PM ET (US) Clark,what did you do to plug up the 1.5"hole?I'm thinking mabye tig weld a plate over it.By the way,do you know if the mid section is aluminum,magnesium or something else? I hope it's not magnesium for safety reasons.
Clark Roberts	posted 01-03-2006 07:45 PM ET (US) Mid-section is aluminum. I covered the hole with a plate via sheet metal screws. Put as much heat on the shaft as you can...also dousing with cold water may help break the bond. Clark... SCN
cbgann	posted 01-03-2006 07:57 PM ET (US) Before cutting the big hole, you might try a small hole flip the engine and use PB Blaster instead of WD40. Good Luck
Brys13s	posted 01-03-2006 08:32 PM ET (US) Yeah,I still might try that as I mentioned on my 01/01/06 thread,so that it can be tapped and plugged with a ss fastener.I'll start small and go bigger if I have to.I would not use WD-40 for this application.PB Blaster,Liquid Wrench,NAPA Penetrating oil or something simmilar would be the choices.I think WD-40 is good stuff if it is used for what it was made for,but that's a whole different topic.