1979 Merc 40hp: removing lower unit....losing my mind!

Drindin

Petty Officer 3rd Class
Joined
Oct 21, 2006
Messages
80
First off, this motor sat outside, uncovered for approx 9 months to a year but supposedly ran just before that. Ok...I have been trying to remove the lower unit from my 40hp for about a week now and I am absolutely losing my mind. I'm about ready to take a sledge hammer to it. Please?!? Can someone tell me how to get this thing off?? I have a manual and parts diagrams but they are not helping.

These pics are from another post but I have numbered them to show what has been done...and what I'm curious about.

First pic: I have removed nuts from 1, 2, and 3 location. 4 & 5, of course, only loosen so much before they top out. Lower unit has to drop more in order to completely remove these.

Second pic: I've read that rust can hold 1 & 2 together pretty well. I've squirted WD40 & PB Blaster, as best as i could, up into the area where these are located (and squirted not just a little). Using a flat-head screwdriver, I've tried prying them apart, wedging the screwdriver as deep as i could to hopefully get them to give way, and even tried the see-saw trick (where I put wood wedges about halfway down each side and used a rubber mallet to smack up on the back portion, waiting for it to give. Nothing. Also, what is #3 AND does #4 have something to do with all of this? If I put a small screwdriver in #4, I can see the cap popping up & down (around the splines, which I haven't seen yet).

Please help me before I commit outboardicide!
 

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MacDaddy21

Petty Officer 1st Class
Joined
Feb 16, 2011
Messages
280
Re: 1979 Merc 40hp: removing lower unit....losing my mind!

I've got a 79 40hp also, and my lower unit was ridiculously hard to get off as well. So you are not alone. What can help you, is to have a friend push the gear selector into forward then neutral then reverse, and back and forth, while you wiggle on the LU. Also, while they are doing that, I found it useful to get a small piece of a 2x4 and a hammer, and place the 2x4 on the cavitation plate, the flat plate directly above the prop, and tap with the hammer. not to hard though. and don't hit on the sides of the gear case. also. you can have someone turn the flywheel while you pull on the lower unit. It is likely that the splines on the driveshaft are just stuck where they mate with the powerhead. Like I said, mine was a b*tch to get off, so just stay patient with it, and try the things I told you over and over until it pops off. When mine came, it literally flew off. The driveshaft splines had some rust on them, which I cleaned off and greased before putting back on. Good luck
 

Drindin

Petty Officer 3rd Class
Joined
Oct 21, 2006
Messages
80
Re: 1979 Merc 40hp: removing lower unit....losing my mind!

MacDaddy, I tried your tips from an earlier post you replied to. The shifting thing did a little something....it shifts easier. Does the shifting rod (that I read about so often) have a nut or coupling that has to be backed off?
 

MacDaddy21

Petty Officer 1st Class
Joined
Feb 16, 2011
Messages
280
Re: 1979 Merc 40hp: removing lower unit....losing my mind!

no, it just has the same spline cap on the end of the rod that the male end on the lower unit meets with. I also used a big screwdriver and pried around carefully while someone tapped with a hammer and wood block or tugged on it. Sadly you really cant get any WD40 or PB where you need it. Most likely, the splines are just rusted and stuck together. It will take a lot of persuading but it will come off.
 

Drindin

Petty Officer 3rd Class
Joined
Oct 21, 2006
Messages
80
Re: 1979 Merc 40hp: removing lower unit....losing my mind!

I've given up. I spent ALL day in 99+ degree weather (106 heat index....whew!)trying to get this *#$!@% apart and it has beaten me. I tried wedges, hammers, screwdrivers, shifting it back & forth (fwd, neutral, rev, neutral, fwd...) while someone beat it, tried using a tie-down strap, ratcheting it, hoping i could pull it apart...nope. Even let a buddy start dismantling things that I KNOW didn't need to be removed. Guess I'll see if the local mechanic will have any luck & show me if he does (this I gotta see!). If not, all is fair in war AND war.
 

MacDaddy21

Petty Officer 1st Class
Joined
Feb 16, 2011
Messages
280
Re: 1979 Merc 40hp: removing lower unit....losing my mind!

That sounds just like mine was. It took me DAYS of working on it though. Not just one or two. I'm talking a week or two and spending 5+ hours a day working it. but, after getting it off and cleaning it up and greasing it, everything down there works just fine. Believe me, I thought mine had me too, but I couldn't see paying a mechanic to do it for me. Then again, i'm just an Aggie student and I dont have cash to blow on mechanics. So I just cussed until it came off.
 

BatDaddy1887

Chief Petty Officer
Joined
Jan 18, 2009
Messages
463
Re: 1979 Merc 40hp: removing lower unit....losing my mind!

Sometimes there is one extra bolt under the trim tab (under cavitation plate).....good luck.
 
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