Help removing outboard lower unit

rgranger · Feb 26, 2017

Wow.... that is a tough place to be. A new O.B. is several grand... so I guess I'd go drastic.

Have you tried a ball-pein (a.k.a. ball -peen, a.k.a. machine) hammer? Tap your way around the seem and see if you can knock loose some of the crud holding it together. Liquid wrench and/or penetrating oils might be a good thing to try also. Maybe squirt on a little each evening before bed for an entire week. Then try knocking the seam with the hammer again. If neither of those things work, you might try some of the compounds used for removing rust. Most of those are phosphoric acid based and will attack oxidized metals. If that is what is holding it together it might lossen it up....If that does not work, maybe take a blow torch and gently heat the seem while gently knocking with the hammer. (Make sure all of the fuel is out of the carb. before you use a torch.)

If you do all of that and finally get it fixed.... you might have to sand and repaint your O.B. but still a lot cheaper than a new one.

Good luck.

Gunni · Feb 26, 2017

Since you are now the Head Mechanic you should purchase the service manual, these kind of tasks are detailed. On my Tohatsu 9.9 4-stroke you first remove the spring pin in the shift rod and then remove 4 bolts that attach the lower gear case to the engine case. The gear case pull down, bringing the drive shaft and shift rod with it.

kloudie1 · Feb 26, 2017

make sure ALL the bolts holding it together are out.. Spray some PB Blaster into those holes and or around the studs after bolt/nut removal.. Don't get the Blaster on the seal where the prop shaft comes out the lower unit, it may damage the seal. Be really patient and do this every day for a week or so.. Using a block of wood between the hammer and the lower unit, smack the cav plate of the lower unit downward place the block so that you are putting down force on the lower unit .. not ripping off the cav plate. This probably will not work the first time but continue to Blast it and smack it .. it will release.. to help, you can tap the upper side of the seam not gently, but not with enough force to break the casting.. tap it all around and put some Blaster on/in the seam.. Patience here will save money .. it may take a month of fiddling to get it to finally release.. Good luck.. Last effort, if nothing seems to be working would be to put ice around the lower unit close to the seam .. let it chill then with a propane torch or a heat gun on high, heat the lower end of the extension casting just above the seam .. the idea is to get a big differential temperature across the seam to break the bond..
EDIT: Gunni and Granger are right on.. I was typing while they were relying

centerline · Feb 26, 2017

what can happen is the drive shaft splines rusts in to the pocket splines of the crankshaft.... sometimes its impossible to separate them without damage.
most manufactures have procedures written for where to drill their larger motors so the shaft can be torch cut.... then the hole has to be welded closed and a new shaft installed... im not sure if there is a procedure written for the small motors.

if the lower unit has wrongly been installed using an adhesive sealer such as permatex #1 or 2, at the joint where it normally would separate, then heat is the answer, but it may burn the paint.

rgranger · Feb 26, 2017

After reading Gunni's post, I think the service manual is probably the better place to start. You (and I) had both assumed your mechanic did the job correctly. But these motors are all so different it is a big task to ask a single guy to be an expert on all of the different O.B.'s out there over the 30 years of time they were made. Do the google thing for your model number and see if you can find the service manual. Then if that doesn't work, try the other things mentioned.

uncledom · Feb 26, 2017

PB Blaster is the best thing to cut corrosion IMHO. I usually use a ridiculously small ball peen hammer to tap the areas I want to break free. It's the vibration not the force. Patient is the key. It will take time. If the top of the drive shaft is stuck in the bottom of the crank shaft that might be a bit more difficult. Also how the shift shaft is assembled might be a problem. The shop manual is the place to start.

uncledom · Feb 26, 2017

If there is studs with nuts and you can put some wood between the top of the nut and another surface it will act as a press to remove the unit. Don't use too much pressure as you back the nut off to create force on the lower unit.

dscribner · Mar 1, 2017

Tom L said:
I have a 1993 Tohatsu 9.9 2 stroke long shaft outboard that needs the impeller replaced. It is spitting out a little water instead of a steady stream. The motor has spent its life in salt water and I don't know when it was last worked on by the previous owner.

I took it to an independent marine repair shop to get the impeller changed. After he worked on it for the whole summer, he said he could not get the lower unit to drop off. It seems to be solidly stuck. He gave it back and did not charge me anything (an honest guy). He says it would cost more than the outboard is worth to fix it.

I have tried to get the lower unit to drop off also but I am afraid to try to hard for fear of breaking something. However, since the professional cannot get it off, I can either use it until the impeller is totally dead and the engine overheats or I can try something drastic.

Does anyone have any hints about what to try? How far can I go before I destroy the motor?

Tom,

Been there, done that . . . bought the Honda 8hp extra long shaft in response. Broke that after 15 minutes use. Quoted $1000 to repair. $50 and 45 minutes and it's like new. Oh, where was I? Yeah, the corrosion inside the bosses of the screws have probably chemically welded the two together. Good luck. I tried it all, including cutting the bolts. Nada. failed. Bought the Honda. Did I mention I broke it after 15 minutes use?

All U Get · Mar 1, 2017

Dead blow hammer, set it in the cold, like Maine, then heat by steam or torch. I tapped the seam with a cold chisel. Let's say you chip the casing and have to fill the hole, can be done. I try about anything knowing that it was headed for the trash anyway.

All U Get

Tsatzsue · Mar 3, 2017

I agree with the dead blow. I used wood shims and pounded them in evenly all the way around. Watch out because it lets go and will take a toe off or worse. I was sitting on a bucket and got a blood blister on my sack! Never again!! That is once the shifter is disconnected. You have to make sure your shifter is in the position to allow the most separation between the sections. I know the best route is to replace the impeller here to prove that that is failing failed but you may want to try running it in a bucket with a couple gallons of white vinegar and water. 2 or 3 to one. That will dissolve all of the sea water scale. I just did that with my two hp Evenrude. Worked great. When I replaced the head gasket I found the water jacket really plugged with crap. Probably the cause of the gasket failing. I cleared the blocked passage. Once rebuilt I ran the motor in the mix till the water got hot. 1/2 to 1 hour. Outboard enema. Worth a try. Weed whacker line or stainless wire in the pee hole to be sure all is out there too. I pulled the hose off and blew it out.

Like Centerline said the shaft splines can fuse in and that could be the end. However you should still be able to separate the sections with a stuck shaft. Enough to get channel locks or a sawzall in there for a last resort. I got real intimate with my 9.9 a couple years ago. Looked like a urinal.

KB
CMDRE NETS

Hydro Therapy · Mar 4, 2017

I just changed the impeller on my 03 Nissan 9.9. The procedure was just as, "Gunno" described. My money is on your shaft being stuck, rusted in place. I would disconnect the 4 nuts and shift rod pin. Once there removed I would pry and beat the lower unit to dislodge the shaft from the spline.

The way I see it, u have nothing to lose. I wouldn't trust the engine with a faulty impeller.

centerline · Mar 19, 2017

Tom L said:
Tried PB Blaster for a week and then a propane torch to heat it I was getting nowhere. I got the rear two studs out after cutting part of the housing but the front two would not budge. I finally decided to amputate by cutting the bolts and the lower unit came off right away. I managed to get the cut off studs out by removing some of the case to expose enough of the studs to allow me to grab them with vice-grips. Now I have to decide if there is enough thread left in the bolt holes to hold new studs or bolts. There is about a half inch of threaded bolt hole left in the aluminum case. I can easily change the impeller now and I think I can get things back together.

short of welding it up and redrilling and tapping, you can install the studs using red loctite... it will help hold the studs more secure, and yet still allow it to come apart with a bit of heat... the next step beyond that is using jb weld or marine tex to glue them in, but that should be reserved as a last ditch effort to get one more life out of the motor....

All U Get · Mar 19, 2017

Blue locktite is removable. http://na.henkel-adhesives.com/industrial/threadlocker-loctite-13445.htm

All U Get

centerline · Mar 19, 2017

All U Get said:
Blue locktite is removable. http://na.henkel-adhesives.com/industrial/threadlocker-loctite-13445.htm

All U Get

the red stuff is too, at about 325 degrees... so a torch is necessary to remove it. but it will hold firmly until it gets hot

uncledom · Mar 19, 2017

Well this is gonna sound really weird but you can rebuild it by installing the studs and then welding in AlumiWeld material at the broken sections. It will allow the studs to be removed in future and you can shape it just as you would aluminum once it's cooled.

http://www.alumiweld.com/

centerline · Mar 20, 2017

uncledom said:
Well this is gonna sound really weird but you can rebuild it by installing the studs and then welding in AlumiWeld material at the broken sections. It will allow the studs to be removed in future and you can shape it just as you would aluminum once it's cooled.

http://www.alumiweld.com/

it would be nice if it could work like that, but the alloy used for the manufacturing of the outboard components needs to have a different welding process... the alumiweld product may stick to the surface of the base metal, but it doesnt "weld" to the base metal... welding is where the process actually melts the base metal as it melts the filler, and the two mix with each other, harden and become one. then if necessary it can be machined back to the specifications required.

and the alloy used in the alumiweld product corrodes quickly, so it would be a poor choice for a marine application.

thinwater · Mar 20, 2017

This method was explained to me by an old guy (about my age now, I suppose, when he told me), and it has NEVER failed me, even on some ancient motors.

Remove bolts and soak with PB Blaster. It always helps. Don't forget the shift linkage and grounding wire.
Take a piece of cardboard and trace a half model of the lower unit just above the cavitation plate. Take you time.
Carve this 1/2 model out of a pair of 4x4s, leaving a 1/4" gap between them. A band saw is nice, but passes across a table saw and a chisel works well too. It doesn't need to be perfect.
Clamp the pair around the lower unit with a pair of large carriage bolts.
Clamp the engine securely and strike downwards with a 3-8 pound hammer. You can hit pretty hard without risk. Alternate sides (fore/aft and right/left).

I've even done this in the water, swimming, under a catamaran.

Help removing outboard lower unit

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