Trouble re-installing lower unit

Help!

Mercury 1999 150hp 2-stroke saltwater series

I took down my lower unit and replaced to impeller with no problem. When trying to re-install the lower unit, I can't get the transmission spline to mesh with the linkage. I've tried it in neutral, reverse and forward and can't get the gears to mesh. What's the trick here? Please help.

New user here.
SunshineFL, I am having the same problem.
I have a 1986 35HP mercury outboard. Removed the lower unit to change impeller. Can't get the lower unit to mate to the upper part of the outboard. Can only get lower unit to about 1/2" from the upper part and that is where it stops. Suspect the shift linkage/shaft, but I just don't know. If I get it figured out, I'll let you know. Maybe it will work for you even if the outboards are different.

If you're a 1/2" apart it sounds like the top gear of the shaft isn't mating with the flywheel. Try turning the flywheel slightly by hand.

Just had my 90 Merc 4 stroke lower leg off twice in the last week, its a PITA, way easier with two people, confirm what gear your in, eg FWD/REV or neutral, on your lower leg before you try and install the lower leg otherwise you will need to remove it again, i believe it default to FWD when removed. in FWD the prop will only ratchet in one direction, neutral spin free, reverse it locks in both directions, i installed mine in the FWD position, once confirmed what gear position make sure throttle lever in boat is in same position, slide lower leg up and you will need to first align the drive shaft spline by turning flywheel (make sure battery is disconnected), once drive shaft aligns you will be able slide it up further to about 25/30mm there it will stop because the gear selector coupling is not aligned with splines, (i placed my gear coupler on the spline coming from the motor) which allows you to see which direction it needs to move on the lower leg gear shaft spline, this is where you need two people to make it easier, so you can get down there with a light to see, (make sure your water pump tube and adapter are aligned at this point also),with the lower spline against the coupler get some pointy nose pliers and turn the lower leg gear shift shaft in the direction it needs to move to align (it will be minimal in either direction). by this stage your second person will be swearing and cursing for you to hurry the *%ck up. once aligned it should mate together and bolt up, before you place all nuts on lower leg confirm your gear selection works in all positions/directions. That is my experience, hope it helps you.

cheers

Got the lower unit on today. The crankshaft was engaging as it should. The water tube was lined up, but the shift splines were not lining up. Got someone on the boat to move the shift lever very slow. The lower unit went on up to about a 1/16" gap. You just have to be careful that the splines are timed properly. Since my boat is going to shop for carburetor work, I will have mechanic check the timing. Hope this helps.
Mac

Yep two people make light work.

I use a bungee cord to take the weight of the LU when 'George' isn't around to help.

Jeff

Also been stuck at that almost in position.
What I've found to work from others on here.
FWD gear position. Plug out so no compression and easier to spin flywheel for that final seating.

Little tip for one person, Take small hydraulic jack and place under foot once lower unit is mostly in place, slowly jack up lower unit while watching and aligning gear shaft and water pump. Do not force jack but you can maneuver lower unit very easily while lining and there is no strain to keep in place while continuing to properly line.

ok Guys- Shift controll @ helm = MUST !! be in forward!! engine - if shift cable was unhooked?? must be installed & in =Forward!! In the old days!! there was a plastic part that fit ocer the shift rod in lower unit - I have even had those indexed in wrong position!! Lube the L U Shift shaft with some grease -Sparingly!! making sure l u =IS!! in Forward also on install. Line up all- should go in fine. Remember =the factory designs dont make it hard for us !! Its just Us making it -Hard!

Hi All, Old thread - but I can add how I get my Lower unit up the last 1/2". Tried and tried - hitting something - metallic. So, I was sure it was not the plastic sleeves for the exhaust and water connections - that left the shift shaft (Taking me FAR too long to figure that out. !! LOL). So I had a thin Hemostat (see below) that I was just able to fit in the space between the lower column and the lower unit 1/2" space that was not closing up. Grabbed the shift post for the gear box and turned it slightly back and forth with up pressure on the lower unit. I've done a few of these over the years with minor issues getting the gear box up tight by hand.... This was a real pain.

Tip ... I did this alone. Dragged a low work table over and under the LU and then used the tilt to raise lower the engine while the skeg of the LU sat on the table. Much better for dinking around. Merc 2018 4S 60hp bigfoot.

AmazonSmile: MABIS Kelly Forceps, Medical Forceps, Locking Forceps, Silver, 5.5": Health & Personal Care

When I try to put my lower unit into place there is a "bushing" in the upper that is causing me to have to trim the motor back down and reach up with a long rod to center the "bushing" then I can slide the lower into place. I'm calling it a bushing but honestly don't know what it is and want to get the replacement part I need but first need know what I'm fixing. If anyone can tell me what I'm having an issue with that would be great.