Help on 1978 20hp mercury

[Midnight Runner]

Help, I got screwed. Can someone help.


A good friend of mine has bragged up this site. A site of guys with great knowledge, wisdom, fortitude and power. Ok, Ok, busted knuckles, tricks of the trade and just flat out creative thinkers. I have just recently bought a 1978 20hp Mercury Outboard. The person I bought it from was able to briefly run the motor but we had no access to a water source to check the water pump. He claimed he had put in a new water pump within the past year. Well as you can guess, I got it home and put it in a bucket of water and not a drop would come out of the pee hole, so I removed the hose and it and the pee hole were clear. Then I removed the plastic elbow from the top of the power head it was clear also. Below the plastic elbow I can look down in the water jacket and it also looks clear. So I have come to the conclusion that it needs a water pump. Well that’s where all the problems started. I have removed the allen screw in the hole in the back top of the lower unit and dropped the plate. I have also removed the nut under the plate and the one at the front of the lower unit and yes you guessed it, the lower unit won’t come off. I have PB Blastered it to death, took a piece of wood and hit it with a hammer on top of the cavitation plate until I have cracked both sides of it, but did not break them off (I’m sure a good welder can fix it) without a bit of movement. I have even cussed and swore at it to try to coax it to come off, but no luck. I have been able to use 5 screwdrivers and have just been able to get about a 1/8 inch gap and I can’t get any more with out extreme force and possible irreversible damage. I think the drive shaft is stuck in the power head. Can someone PLEASE throw some ideas my way on how I can get the drive shaft unstuck from the power head.<O:p</O:p
<O:p

Thanks in advance for all your help<O:p</O:p

<O:p></O:p>

Midnight Runner <O:p></O:p>

[SUPAJAY]

Did you disconnect the shift linkage ?

[The Big Al]

I know that feeling! Someone ask! DID you do this! And you just have this blank look on your face! Man it just hurts!:o

[The Big Al]

go to this leak and see if this break down will help !


Good luck.

Al
Click below!
http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=%2075538&ivar=images/MERMAR/75538/26.png&inbr=481&bnbr=16&bdesc=GEAR+HOUSING+ASSEMBLY%2C+COMPLETE+%28PAGE+1%29

[Riverracer280SS]

I have seen this 20 Merc , and the shift linkage is splined like the big engines.
So there is No Disconnecting the linkage..... It should just slide down.
If The drive shaft is frozen in the crank what is the best way to approach it from here? (NOTE): It's been soaked with blaster for over a week now , and it AIN"T MOVING! Can We heat the Driveshaft?
Thanks

[The Big Al]

also this is break down of mid section


http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=%2075538&ivar=images/MERMAR/75538/23.png&inbr=481&bnbr=15&bdesc=DRIVE+SHAFT+HOUSING+ASSEMBLY

[Midnight Runner]

Did you disconnect the shift linkage ? Well the shift linkage is splined and fits into a plastic shift shaft and it moves freely in and out. what tiny bit I can move it.

[Bruster]

Been there and done that (this). This is drastic. :eek:
Pry the housing and gearcase apart enough to get a sawsall between and cut the driveshaft, waterpump housing etc. in half. A good blade will make it happen. Go slow at this slow so you will not damage the housing or midsection. Now you can remove the powerhead and heat the shaft up and get it out. Find another driveshaft or complete lower unit and put it together. Complete lowers are on eBay for $100 or so. :D

[Midnight Runner]

go to this leak and see if this break down will help !


Good luck.

Al
Click below!
http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=%2075538&ivar=images/MERMAR/75538/26.png&inbr=481&bnbr=16&bdesc=GEAR+HOUSING+ASSEMBLY%2C+COMPLETE+%28PAGE+1%29

Thanks for the break down on 20 merc it will help. the parts manual is about $70.00
thanks for your help.

Midnight Runner

[Midnight Runner]

Thanks for the break down on 20 merc it will help. The manual is about $70.00
tahnnks for your time.

Midnight Runner

[Bruster]

Thanks for the break down on 20 merc it will help. The manual is about $70.00
tahnnks for your time.

Midnight Runner

eBay Mercury manual...

http://cgi.ebay.com/ebaymotors/MERCURY-OUTBOARDS-SERVICE-MANUAL-4-4-5-7-5-9-8-20-40HP_W0QQcmdZViewItemQQcategoryZ26453QQitemZ4586529258QQrdZ1QQsspagenameZWDVW

[1500_xs]

I had a similar issue with my 20 merc. I put it in a bucket and it wouldn't pee. It was because the gearcase was only in the bucket. The motor needs to be in the bucket pretty deep before it will pee (ie submerge the water pump). If you did this (or hooked it up to muffs - that works) and it still won't pee I guess you need a water pump.

If you took off the bolt at the back of the gearcase along with the three up front I am not sure what the problem could be. I've had stuck shift shafts and they will pull out of the gearcase before the casing will break. When looking through the little gap you made see if the driveshaft is moving or if it is just pulling from the gearcase. If the driveshaft is stuck I can't see it moving a little and not the rest of the way. If really in doubt try pulling the powerhead before you cut anything. If it won't come off then you know it is indeed stuck without wrecking a good drive shaft.

PS. those gearcasae shells are pretty common. You can probably replace the casing for less than a weld job.

hope if works out for you!

[Midnight Runner]

Thanks Bruster. I was afraid that I might have to do major surgery on this 20 merc. By heating the drive shaft that will allow it to be removed? Do you think I will have to do any drilling out of the driveshaft to remove it from the powerhead?

Thanks
Midnight Runner

[Bruster]

Thanks Bruster. I was afraid that I might have to do major surgery on this 20 merc. By heating the drive shaft that will allow it to be removed? Do you think I will have to do any drilling out of the driveshaft to remove it from the powerhead?

Thanks
Midnight Runner


Heat the driveshaft up real good (red hot) a couple inches up from the crank.
It'll surcumb to the heat with a little tapping from the hammer. :eek:

[Midnight Runner]

Thanks for the info 1500 xs. I will try unbolting the power head next and see what that gives me.

Midnight Runner

[Midnight Runner]

Heat the driveshaft up real good (red hot) a couple inches up from the crank.
It'll surcumb to the heat with a little tapping from the hammer. :eek:

I will try the heat in the next couple of days. Thanks for all your help.

Midnight Runner

[sosmerc]

I feel your pain...I've been there many times with older Mercs that were NOT serviced properly during their lives.
I have seen driveshafts so badly "corrosion-welded" into the crankshaft, that when you finally do get it out, there are no splines left in the crank. All of this grief could have been avoided had the owner followed Merc's recommendation to annually remove the lower unit so that the splines can be greased and the impeller changed. They also recommended that the bearing carrier be pulled out as well for lubrication...I don't think anybody every did that.
Sometimes you have to take a hole-saw and drill a hole up near the top of the driveshaft housing close as possible to where the driveshaft enters the crank. Then, with the engine upside down resting on the flywheel, heat the driveshaft as hot as possible and then spray Kroil or other penetrating oil down into the area where the shaft goes into the crank. (continue pressure with wedges between the gearcase and driveshaft housing during this process).
If all else fails, cut the driveshaft. Then you can pull the lower unit, but will still have to pull the powerhead and deal with the stuck shaft. With time and heat, it WILL come out...but as I said earlier, sometimes there isn't much left of the crankshaft splines.
Good Luck!

[Midnight Runner]

Thanks SOSMERC. Is there any special lube I should use on the drive shaft when I reinstall it. That is if the splines are not shot.

Midnight Runner

[sosmerc]

I use Mercury 2-4-C, but I would think just about any grease with teflon in it would work. The older 20hp is notorious for difficult lower unit removal...the lower unit needs to come off at least every year...and you must lube all the shafts, studs and splines!

[Midnight Runner]

Thanks for the lube info. I had to cut the drive shaft and you were rite, it is part of the crank. It looks like someone stored the motor upsidedown by looking at the top of the cowl and the inside of the cowl. So being upside down the water ran down the shaft to where it fits the crank and now I have a the mating of 2 metals, to 1 chunk of rust. I was thinking of drilling down the center of the driveshaft where it go's into the crank (but not drill into the crank) to weakin the drive shaft, ad a little heat and then break off the the drivshaft spline pieces that fit into the crank. I'm trying not to mess up the crank or the crank seal if possible. Think this might work? any other suggestions.

Oh, and thanks for your time helping with this new project.

Midnight Runner

[sosmerc]

I don't know about drilling the shaft, it's not something I would be able to do.
I'd try soaking it for a few days in a penetrating oil like Kroil. If you could weld something on the end of the shaft so you could use a slide hammer...that might get it out faster. But soaking and heating, soaking and heating...it's not alot of fun.

[Midnight Runner]

Ok sosmerc, I have made a home made puller to keep pulling presure on the driveshaft as I'm soaking and heating, soaking and heating. I'll let you know in a few days if I get any results.
Thanks again for all the help.

Midnight runner

[Bruster]

Again.....

Heat the driveshaft up real good (red hot) a couple inches up from the crank.
It'll surcumb to the heat with a little tapping from the hammer.

You'll need an acetylene torch to get the shaft very hot very fast.

[capnzee]

Unless your time is worth nothing, I think it would be cheaper to replace that old Merc. Next time, test your motor in a 50 gallon drum filled all the way up to the bottom of the clamp brackets! A bucket won't cut it-outboard water pumps are usually not self-priming and need to be submerged to operate properly. You used a bucket and now have a bucket of worms, sorry, :( Capnzee