lower unit won't budge

[turtles11756]

hello, i have a 1970' merc 50hp that was used in salt water thou i doub't corrosion is holding this lower unit on . all the bolt's have been loosened including under trim tab but this thing won't budge to separate from the drive shaft housing.the lower unit is totally shot and may never have been maintained over forty years from the looks of it. but the power head is all original with even compression 132psi-125psi and a strong spark . any ideas how i can separate lower ?. i have been hammering away and it has not come down even a fraction .thanks

 

[smsscuba]

Re: lower unit won't budge

Have you loosened or disconnected the gear linkage?

 

[crem1]

Re: lower unit won't budge

Did you put it in forward gear? If so and still stuck then it's corrosion, start off with Deep Sea foam, apply it and let it sit for a day.

 

[turtles11756]

Re: lower unit won't budge

the lower unit should drop down no matter which gear the shifter up top is in no ? shifter is jammed in reverse so i can't just shift the gear

 

[crem1]

Re: lower unit won't budge

Many people forget to put it in gear, then initiate the corrosion removal process

 

[RLT III]

Re: lower unit won't budge

try using a thick gauge scraper(with the bevel facing towards the lower unit) with a little oil on it and working around the unit with a hammer a few hits at a time

Good Luck

 

[turtles11756]

Re: lower unit won't budge

the darn thing shifted into forward gear. prop shift shifted into forward too can't believe it the gear case was filled with gasoline and water when i brought it home. I'm hitting on the lower unit with a hammer and 2x2 but it still holds tight

 

[crem1]

Re: lower unit won't budge

As I said earlier, spray it with Deep Sea Foam and let it sit for a day

 

[JustJason]

Re: lower unit won't budge

Is it dropping at all? even like 1/2 an inch? FWD Gear isn't always enough on these small outboards, sometimes you have to pull a carb off to disconnect the shift linkage.


The other thing to is, if this lower hasn't been off in a dogs age, the driveshafts can and will rust solid into the crankshaft.

 

[Texasmark]

Re: lower unit won't budge

The other thing to is, if this lower hasn't been off in a dogs age, the driveshafts can and will rust solid into the crankshaft.

You know Jason, I had always seen SS shafts on engines I had been into/seen into until one day in about 1965 I was in a Merc shop for something and I saw a 90-100 hp range lower unit sitting in a vise and the driveshaft was the most horrible looking thing I had ever seen....all rusted and scaled up.....obviously a salt water use engine and obviously a carbon steel shaft.

That really turned me off Merc for a long time to think that they were that stupid; I just couldn't believe it. Course later they came to their senses and made all their shafts SS like they should have been from the start and then problems like this wouldn't have occurred.

Mark

 

[turtles11756]

Re: lower unit won't budge

no the lower unit hasn't dropped even a fraction. if it's rust on the splines drive shaft to crankshaft is there away to get them apart ? i might try the shift link removal but i think the splines are holding it up. thanks, guys i,m gonna take my time with it

 

[Texasmark]

Re: lower unit won't budge

I asked myself just that question yesterday: if it is the shaft stuck, how do you get to it?

I thought about just turning it upside down and pouring diesel down the exhaust, but I don't know if the shaft/powerhead interface is open to exhaust, especially with tuned exhaust engines and also I don't know that it wouldn't wind up in the engine via the exhaust manifold which one surely doesn't want. So I don't think that is a good idea.

I also thought about getting the LU and midsection to separate by twisting the LU but as I recall there are alignment pins between the two that keep it from twisting.

Well, maybe one of these guys that work on salt water engines will jump in and come to the rescue so just keep bumping it up till it gets adequate attention.

Best I can do,

Mark

 

[JustJason]

Re: lower unit won't budge

Your not going to like the answer....

You use a big old hole saw right in the middle of the extension case (or driveshaft housing, depending on what ya call it)
Then you cut the driveshaft in half with sawzall.
Drop the drive, get up in there and wiggle and beat the driveshaft untill it comes out.
Install a new driveshaft in the lower unit.
Clean out the end of the crankshaft the best you can with a gun brush and a cordless drill, followed by compressed air.
Weld or braze the plate that you made with the hole saw, followed by some epoxy in the center hole. You can leave it rough or spend some time and clean it up. It doesn't matter if it's water tight or not, just want to keep the growth out of the driveshaft area the best you can.
Grease everything, and re-install the lower unit.

 

[Texasmark]

Re: lower unit won't budge

Your not going to like the answer....

You use a big old hole saw right in the middle of the extension case (or driveshaft housing, depending on what ya call it)
Then you cut the driveshaft in half with sawzall.
Drop the drive, get up in there and wiggle and beat the driveshaft untill it comes out.
Install a new driveshaft in the lower unit.
Clean out the end of the crankshaft the best you can with a gun brush and a cordless drill, followed by compressed air.
Weld or braze the plate that you made with the hole saw, followed by some epoxy in the center hole. You can leave it rough or spend some time and clean it up. It doesn't matter if it's water tight or not, just want to keep the growth out of the driveshaft area the best you can.
Grease everything, and re-install the lower unit.

Midsection, per my Merc manual............I thought it would come to something drastic like that but apparently it works and it is cheaper than a new engine.

So I guess he is going to get a new water pump and new lower unit seals in the process. Sounds like a deal to me if he has the time, knowhow and $$ to fix her up.

Mark

 

[sschefer]

Re: lower unit won't budge

Mark it took them a while. I just pulled apart a 99 200 Blue Water with a carbon steel swivel pin. When I took the exhuast plate off the mid dropped to the ground. You can't get a carbon steel swivel pin anymore, they only sell the stainless version now and it's almost $600.00.. I have to wonder how many screwed up transoms Merc had to pay for before they realized their error.
I suspect there were quite a few and the cost of the new pin is how they're trying to get their money back

 

[blue90HP50]

Re: lower unit won't budge

Turtle: Are you sure all bolts are out? 2 Side studs with nuts, one bolt screws up into midsection from underneath, and then the trim tab bolt. Did you miss the one from underneath? If you're sure all are out then snug-tighten the nuts on the side studs, find or purchase two larger nuts and place one above each stud. These should be close to the midsection flange above where these lower unit studs protrude through into the midsection. Back the snug-tightened nuts back off to to press larger nuts against midsection flange. This puts "Vertical" pressure on lower unit. Be careful and patient, add more pressure daily. Maybe lower unit will release in a few days. Also, spray PB Blast all around mateing surface where LU meets Midsection to start this process. Good Luck!

Blue

1970 Merc 500 running again after 22 years on it's side on dirt floor.

 

[199675hpforce]

Re: lower unit won't budge

Did you pull off sacrafical anode? There maybe a bolt under there. Also hit lower unit with rubber mallet get ready to catch it!

 

[turtles11756]

Re: lower unit won't budge

RLTIII i was able to get a scraper between the lower unit and drive shaft housing toward the front .it even separated a fraction but the back is holding tight as if i did forget the bolts under trim tab but every thing has been loosened .gonna try to put something above side mount bolts and bring pressure between the two like blue90hp says. no hurry, the more i look at this motor the thing probably never was taken apart in forty years since new

 

[Chris1956]

Re: lower unit won't budge

Turtle, Can you spray some PB Blaster into the midsection? Do you think you can hit the driveshaft? If so, hang the motor upside down, 1 " off the floor, and spray her good. See if the oil and the weight will work the criveshaft out of the crank.

Second alternative is to disassemble the gearcase, and remove the pinon nut. Then if you can cause the waterpump housing to crack, the driveshaft can stay in the crank, and the gearcase can come off.

 

[Texasmark]

Re: lower unit won't budge

Second alternative is to disassemble the gearcase, and remove the pinon nut. Then if you can cause the waterpump housing to crack, the driveshaft can stay in the crank, and the gearcase can come off.

Now that's a slick idea. If he bored a hole in the midsection and cut off the driveshaft, he would have to go into the lower unit anyway and undo this same nut so he hasn't lost anything. Very nice.

Mark