Lower unit removal

[Randy Skopinski]

I started to change out the water pump on a 1992 25 HP Johnson OB motor but cannot get the lower unit to come off. I have removed the 4 bolts on the sides, the forward nut and disconnected the gear shift connector and plastic insert and nut. The aft end of the casing is free and can be pried open easily ~ 3/8" but the forward end (toward the boat) WILL NOT BUDGE. I even placed a piece of flat bar above the nut and screwed the nut up aginst the flat bar pushing down on the lower casing wit a lot of force. Nothing will move. Can the spline shaft connection be that frozen up? Is there any other means of freeing up this connection or have I missed something that is a secret?

Randy

 

[Cofe]

Re: Lower unit removal

Welcome to iboats Randy!
That front stud goes through a steel bushing inside the unit. Spray PB Blaster liberally on that stud and if you have a torch, heat that stud up. The use of wooden door jam wedges will help to separate the unit. The spline shaft could be stuck in the power head, and about the only to try to get it loose is to suspend the whole motor upside down with the flywheel about a half inch off of a piece of wood on the floor. Spray lots of PB Blaster into the front half of any gap you can get between the mid section and the lower unit. This will let the PB run down the shaft into the splines on the power head. Have patience, and maybe let it soak over night. Sometimes they can be difficult. Good Luck

 

[Randy Skopinski]

Re: Lower unit removal

The frozen spline theory makes the most sense. I will give this a try, thanks. I ran the motor for a while to see if that would help break something free & loosen something up.

Randy

 

[boobie]

Re: Lower unit removal

Have you tried any heat on that stud as Cofe suggested? If you try any heat use either mapp gas or an acy/oxy torch. You can also drive a good sharp putty knief in that forward seam.

 

[Randy Skopinski]

Re: Lower unit removal

After working on it for a few hours today I am convinced tha t it is hung on the 5/16" stud on the forward end. That sucker is some stuck! I work on 100,000+ HP gas & steam turbines & this though much smaller than a 3 or 4" bolt is every bit as tough! Because it is so small & I do not want to break something it makes it every bit as frustrating! I even got an air hammer & and being VERY careful banged around on the thick section (on a metal plate) with no successful results. I have got the back to open enough that I can see the stud and could probably cut it off with a hack saw blade but I don't want to go there just yet. What have you found to be the best penertrating oil? In the field we find that nothing works all of the time but KROLL seems to work as well as anything. What I need is someting slightly acid to dissolve the crud without wasting my casing. Just a good thing that I don't have to use it anytime real soon.................
Randy

 

[boobie]

Re: Lower unit removal

Try acetone and ATF mixed 50/50 in a squirt can. It's better than Kroil. And a lot of patience.Down in SW FL we use a of lot heat dealing with salt water mtrs all the time.

 

[dew2]

Re: Lower unit removal

Something slightly acidic would be white vinegar,Then the kroil(my choice) Never tried the 50-50,But I dont like acetone's dangers,Dont think I ever saw PB blaster heard of it here.

 

[Cofe]

Re: Lower unit removal

Randy, something else to try is to get some thin nuts, and double nut that stud and try to unscrew it from the housing.
Kroll is good stuff, PB is good stuff too. The acetone/trans fluid is also very good. The thin properties of acetone helps to get into tight areas. Since you work on turbines, you should know how helpful heat is in removing stubborn bolts, nuts, seats etc. In my past life, I too worked on turbines and power plant equipment of all sorts.
PB Blaster and heat is my favorite for tight, rusted, corroded, and galded stuff. PB can now be found at Wall Mart in the auto section.

 

[78 mckee]

Re: Lower unit removal

It is most likely that the steel bushing is frozen / corroded into it's location hole in the upper part of the exhaust housing. I would use propane heat on the upper part around the stud to try to free it. Using a propane torch you will not be able to get it hot enough to damage the aluminum.