Can't separate lower unit on '84 25hp long shaft Evinrude

[NWZFAN]

I bought an older boat with a 1984 25hp long shaft Evinrude that has not been maintained. I have loosened all the bolts and separated the shift rod. My first question is, do I want to separate it above or below the extension section. It appears that the main bolt is frozen. I've been dribbling PB Blaster on the bolt end for weeks and it does seem to ooze in, but still no movement. I've tried smacking it hard with a large rubber mallet. Nothing. I have a very slight gap (razor blade) except where the main bolt goes through on the rear. One guy suggested that I need to heat it up real hot with acetylene, which I don't have. I only have the small propane can torch. Any ideas? (the black band is a bungy cord)

Thank you
Ken

 

[F_R]

Ideally, you would separate it below the extension housing. but right now it isn't that important. That rear stud bolt is the problem. Personally, I'd do as suggested and use an acetylene torch t get it hot enough. A wedge on top of the stud may persuade it. May also bugger up the threads.

Put away the mallet. All that will do is break something. If all else fails, and as an absolute last resort, take a hacksaw to the rear of the extension and cut through the stud bolt. Saw cut can later be welded and stud replaced.

 

[NWZFAN]

Thank you. I may have to take it someplace that has a torch. Does that bolt have threads on both ends? One end screws into the gear housing and the other sticking out with a nut? Do you think it would help to try and lock two nuts together on top and try to turn/ twist it? One more reason for changing the water pump regularly.

 

[racerone]

The shank of that stud is likely jammed with corrosion.-----Try a small propane torch to get that area HOT so you can turn that stud with the jam nuts.-----That may break the bond.------Or perhaps the driveshaft is jammed in the crankshaft by RUST from the carbon steel crankshaft.-----Maybe tomorrow folks will start maintaining fine machinery, but I doubt it.

 

[kbait]

Yep..stud is threaded both ends (different thread counts, I recall). If you have space to lock two nuts together, give it a try..add what heat you can to the surrounding metal. If the stud turns at all, it will likely have broken the corrosion and will then separate normally.
Good luck!

 

[kbait]

Racer beat me.. that’s why he’s racerWON!

 

[racerone]

I have dealt with stuck lower units.-----And more than one of this model 25 HP too.

 

[NWZFAN]

I hope this isn't a silly question, but are "jam nuts" a product or just the procedure of getting two nuts to tighten onto each other? I'm trying to understand what gives them the ability to turn the bolt and not just rotate up the threads. have some car mechanical skills, but not so much with outboards (some, but not much). Thanks again for your replies.

 

[F_R]

Yes, two nuts "jammed" together. Ain't going to work, but try it if you want. Does NWZFAN stand for New Zealand? Seems like some of the saltiest motors in the world live there, from what I've read..

 

[NWZFAN]

Yeah, progress! I used heat and a wedge and was able to get about 1/4 inch gap. Now it seems the resistance is towards the front (driveshaft?). Any ideas on freeing that up? I saw a YouTube where a guy had a similar situation and turned the motor upside down and sprayed an entire can of degreaser into the shift rod hole and let soak for days.Do you guys think this is a viable effort? The separation is above the long shaft extension, not the lower section between it and the gear case. Looking for some good advice. Thanks. Ken

 

[NWZFAN]

NWZFAN is for "Northwest Z Fan" as in Datsun 240Zs. Had 9 at one time. Still have two. I live in the Tacoma, WA. area. Off topic. Sorry guys.

 

[Grub54891]

Yeah, progress! I used heat and a wedge and was able to get about 1/4 inch gap. Now it seems the resistance is towards the front (driveshaft?). Any ideas on freeing that up? I saw a YouTube where a guy had a similar situation and turned the motor upside down and sprayed an entire can of degreaser into the shift rod hole and let soak for days.Do you guys think this is a viable effort? The separation is above the long shaft extension, not the lower section between it and the gear case. Looking for some good advice. Thanks. Ken

Some will come apart after soaking in penetrant for awhile, some don't. Had one that just would not come apart. Had to cut the shaft, pull the powerhead and it still would not come out. Slide hammer would not work either. If it comes to cutting the shaft, make sure you have a spare.

 

[NWZFAN]

Before I turn this thing upside down and dump solvent/degreaser down the shift rod hole, can anyone tell me if the liquid will actually cover the spot that I am attempting to free up? Not know the construction, don't want to have it all simply drain out before doing its job.I plan on hanging it from a strap of a catch pan, but still don't want to waste a can of goodness by having drain right out. As for a spare drive shaft, nope. (

 

[F_R]

Wise to question it. No, you can dump all the stuff you want in there and it will NOT reach the problem. The problem is the drive shaft is rusted into the crankshaft splines. The drive shaft runs in an isolation tube, protecting it from the exhaust environment. Dumping liquid into the exhaust, which is what you are proposing, will not enter the isolation tube, nor the rusted splines. Where it will go is into whichever cylinder which the exhaust ports happen to be open, taking a bunch of carbon and crap with it.

If you truly want to try the procedure introduce the magic potion into the big isolation tube drain holes, found near the lower motor mounts. It might work, might not, depending on how badly it is rusted.

Last ditch resort is go ahead and remove the lower unit by brute force. The shaft will either come out of the crank splines or it will pull up out of the water pump, maybe destroying the pump housing as it does. Then, at that point you still have to deal with getting the shaft out of the upper splines. Maybe beat it out with a slide hammer or even pull the power head.

Been there and dealt with it.

 

[NWZFAN]

Thank you so much. What a waste that would have been and possibly destructive. I am not familiar with the drain holes you refer to. By "lower motor mounts, do you mean where it mounts to the boat? Any ideas on how to use brute force without destroying anything external? I guess on of those hydraulic spreaders that car body guys use might be helpful. Agree? I may know a guy with one.

 

[F_R]

I never thought of those spreader things. They certainly do exert brute force, that's for sure. I once watched the EMT's tear the whole top off a car that way. Be awfully careful, those aluminum castings will break.

 

[NWZFAN]

Thanks for the diagram. Just realized that the spreader will not fit into a 1/4 gap. I'll let you know what I end up doing. Pretty cold and wet here in Tacoma area. Might not get to it for a bit.

 

[oldboat1]

Try a flat pry bar and move it around gently prying up and down.

 

[Bosunsmate]

Yes, two nuts "jammed" together. Ain't going to work, but try it if you want. Does NWZFAN stand for New Zealand? Seems like some of the saltiest motors in the world live there, from what I've read..

We sure do, especially in the north where the waters warmer due to that speeding up the rusting process, ive seen new cars that launch boats written off in two years, but they arent the most thorough wash down owners. Perhaps we have higher salinity here.
Cow dung is the worst for car corrosion so I never buy a used farm vehicle and never buy a car thats lived near the nz coastline is another ole saying
My first car was a datsun 140J that was removed from the road due to rust. Police use to pull me over every few minutes due to its old gangster look

 

[NWZFAN]

Sorry for the late update. I finally got them separated with a wood splitting wedge between the top nut/bolt and a big hammer. Bought a rebuilt lower unit and all is together now. Waiting for winter to end before actually using it. On to taking Christmas light down. ;o)