Remove an Outboard Lower Unit with a Stuck Drive Shaft

Screwdriver and crowbar removing outboard lower-unit

After sinking a significant amount of time and money into this motor, I wanted to do one more thing before starting it up. IT had shown a weak stream of coolant when I had run it before, so I figured a new impeller would be the next think to do. I went through the normal routine of dropping the lower unit and had it at the point where it should drop right off. It wouldn’t budge, not a fraction of an inch. After some investigation I concluded that I had a stuck drive shaft. The drive shaft had either seriously corroded or the old grease on the splines had hardened so bad where it met the engine that it had welded itself together. I had a stuck drive shaft.

Possible Solutions to a Stuck Drive Shaft

There’s not a lot of information on pulling a stuck lower unit off online. A good deal of what I found was focused on cutting the drive shaft to get the lower unit off. This would be followed up with getting the shaft off with a slide hammer and then getting the shaft professionally welded together. That was way too much considering the age of the engine and what it would cost.

I found a few promising solutions that I wanted to try before declaring this a loss. One suggested spraying penetrating oil up into the area where the drive shaft met the engine, I tried that for a few days. Others suggested putting some heat on the joint with a torch, I passed on that one. A few of them said to turn the engine upside down so that the penetrating oil could soak into the junction. That one piques my interest. That’s not unusual, my DIY traits seem to lean towards the more difficult paths!

Removing the Lower Unit with the Stuck Drive Shaft Out

The first thing I did was squirt some free all up into the driveshaft joint and then tap it with a long bolt and a hammer. I wasn’t aggressive, just some light taps to vibrate the joint and hopefully, let some of the penetrating solvent in. The spray and tap went on for about three days. During that time frame, I kept designing (in my mind) a gantry made up of 4×4’s and lag bolts. That would be an ideal solution to hanging the engine upside down. After all, why do anything half-hearted. I almost convinced myself to do one. Why not? That would be a great DIY post in itself!

Eventually, reality set in. I wanted to get this engine in operating condition soon. Like in the next week! I still have all of the glass work to do on the 13′ Boston Whaler, and the longer I delayed getting the engine going, the longer it was going to take to tackle the whaler. So, letting reality set my course, I tipped the engine over on its head.

Turning the Outboard Upside Down

Blocked upside down outboard stand
Blocked upside down outboard stand

Just to be clear, I didn’t just flip the entire engine over. What I ended up doing was pushing the engine stand over and laying it down sideways. I kept the engine on the stand, taking it off the stand opened up a whole realm of possible disasters. Once the stand was on its side, it was a simple matter of turning over again, so that the outboard was bottom side up. 

I did lift the stand up by bracing some paving stones on the longest points. This didn’t entirely take the weight of off the cowling, but it did lighten the load on it.

The Next Steps

Once I had the engine upside down, I began a repetitive process to get the drive shaft loose. The first thing I did was to get a flat wrecking bar and a fairly think screwdriver. The screwdriver was used to wedge the front of the lower unit. The front had a little bit of a gap but I could not use anything larger than the screwdriver. The housing for the shift lever was in the way.

Stuck Drive Shaft view of shaft
Stuck Drive Shaft view of shaft
Not a lot of space for a wedge
Not a lot of space for a wedge

So I had 3/8″ maybe 1/2″ of space to get the screwdriver in. I got the screwdriver in and with what little remaining gap there was. Next, I inserted pry bar in the gap at the back of the engine. Once both of these were snugly in place, I used a hammer to gently tap them in further. The goal is to put some upward force on the drive shaft away from the socket it is stuck in.

Spraying Free All on stuck drive shaft
Spraying Free All on stuck drive shaft

Now that the pry bar and screwdriver are wedged in place I can begin trying to loosen the drive shaft. I used a penetrating oil spray called “Free All”. This stuff is pretty amazing and out performs any other penetrating oil I have tried in the past. I sprayed a small amount of Free All into the joint and then using a long bolt and hammer, gently tapped the sides of the drive shaft. The goal here is to provide a bit of shock and vibration to help the oil penetrate into the joint.

Spray, Beat and Repeat

This began a series of spraying free all into the joint, tapping on the drive shaft and driving the pry bar and screwdriver in. I didn’t try to force them in all at once, just a fraction of an inch each time I did this too put some upward force on the driveshaft. This went on for a few days, at least once a day, sometimes twice. On the fourth day, I gave it a “treatment” in the morning.

Tapping on stuck drive shaft
Tapping on stuck drive shaft
Stuck drive shaft removal success
Stuck drive shaft removal success

Went I went to give it a second treatment in the afternoon, I was greeted with a pleasant surprise. After spraying and tapping, I gave the pry bar a light tap and the drive shaft popped out! That was a big relief for me. I still had a few broken bolts to deal with, but the biggest problem I was facing was now solved!

Now it’s on to getting the broken bolts off of the middle unit. First though, what can we do to prevent this from happening in the future?

Preventative Maintenance

Dropping the lower unit should be done on a regular basis to prevent this. I’m not a marine tech but I’ll offer my guidelines on this. If you take your outboard out in saltwater environments, you should drop the lower unit at least once a year. Drop it even if you don’t need a new impeller (although this would be the ideal time to put one in). Once you have the unit off, clean up the splines on the drive shaft. Put a fresh coat of marine grease on the splines. Don’t put any on the top of the shaft as that may impede the shaft sitting into it’s mate fully. Clean up the mounting bolts before replacing them.

Johnson calls for using OMC gaskets sealing compound on the mounting bolts. Seeing as how I had such a rough time getting these off (three of them broke) I am rather dubious of gluing them in. I even contemplated using nickel based anti-seize but instead compromised and used blue loctite. Loctite blue is intended to hold things together and to come apart easily with standard hand tools. I made sure all of the threads on the bolts had a thin coating of this. What I was shooting for was a barrier to keep the bolts and the middle unit from corroding together.

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