Advice needed on dropping lower unit.

steviecops · Jul 2, 2004

Hi I've got to replace the water pump on my 1974 20 hp Mercury. My manual is on order, but won't be here for two weeks. I know that dropping the lower unit on these old Mercs can be a nightmare, so I want to spend the next two weeks preparing for the job to make it easier when my manual gets here.

What parts should I start soaking with penetrating oil? Are the any other tips or advice that might help? I know I'll probably have to beat the hell out of it to get the drive shaft free, but if I can, I'd rather use the softly, softly approach!

P.S. I think the reverse lock is stuck or something too, because I can't move the tilt mechanism

I'd appreciate any advice. Thanks Steve

boatster · Jul 2, 2004

Re: Advice needed on dropping lower unit.

Hi Steve, did you run your motor in saltwater? Because mine was. As you might have read in my post the driveshaft is fused to the powerhead due to rust. Of course I was the proud new owner of this vintage hulk. The previous owner(s) probably didn't replace the impeller for ages. By the time I got to it, it was a small nub with some nubs for vanes. If I were to do it again on my motor I would have made an access through one of the circular shock mounts and cut the driveshaft in half. Then i'd be able to seperate the upper, mid, and lower sections. Once seperated I would begin the (maybe impossible) task of convincing the driveshaft to come out of the powerhead, then get the sucker rewelded. But in your case, your best using some penetrating oil then using hardwood wedges on the lower unit to hopefully convince the sucker apart. Good luck. Adam

steviecops · Jul 2, 2004

Re: Advice needed on dropping lower unit.

Thanks Adam I read through all of your thread, and admire your determination. Like you, I've just got this motor. I got it really cheap, as a spares motor really, but the previous owner told me that it starts and runs well, but just doesn't pump water. It has been used in salt water, but it doesn't look as if anyone has tried to remove the lower unit, so I thought I'd try to get a new water pump in there and make it a good motor. I'll bear in mind your suggestion about cutting the drive shaft, but someone on your thread mentioned inverting the engine and somehow sqirting penetrating oil onto the drive shaft. Do you know where I could get the oil in? Maybe 2 weeks of soaking might make it come away easier? Thanks Steve

boatster · Jul 2, 2004

Re: Advice needed on dropping lower unit.

Steve, yours sounds exactly like my situation. First: there are three bolts required to remove the lower unit, 1 at the front, 2nd under the cavitation plate in front of the anode, and a third under the anode. You need to remove the anode with a hex. After that in theory it should drop down. I'm imagining yours is gonna be tough. Lets hope not as tough as mine. One way you can get oil onto the driveshaft is take the motor off of the transom mount and drill a hole in to the midsection Right inside one of the shock bumpers would be the best location. That way you wouldn't have to do anything but put the rubber shock back on after your done. This is of course assuming you can't get the lower unit off. Good luck. I'm hoping yours isn't like mine. Its definitely a sad way for these sweet motors to go. Adam

KCLOST · Jul 2, 2004

Re: Advice needed on dropping lower unit.

You guys have much more experience with these smaller motors than I do, so take this with a grain of salt... But if it were me, I'd try to pull the power head off first (assuming the lower unit is seized on) before drilling any holes anywhere... Mount the motor on a stand of some sort so you can work from the powerhead and lower unit both... If you can work the powerhead loose, the lower unit will be much easier to pull.

NathanY · Jul 2, 2004

Re: Advice needed on dropping lower unit.

Just make sure that you put the motor in Forward gear before you drop the lower unit, and dont mess with the shifter shaft once you have the lower unit out. Are you assuming that the lower unit is stuck, or have you tried to drop it? If it stuck, lightly rap on a piece of pine on the cavitation plate. Should come right apart.

Keith Buchanan · Jul 2, 2004

Re: Advice needed on dropping lower unit.

Oh no!! Sounds familiar. Here we go again.. Best of luck Keith B...

quantumleap · Jul 3, 2004

Re: Advice needed on dropping lower unit.

I wouldn't cut anything until you see if it comes off in the traditional manner first!!

steviecops · Jul 3, 2004

Re: Advice needed on dropping lower unit.

Thanks for the advice. I haven't actually tried to drop it yet, so I don't know just how bad it's going to be. I won't start to try until I get my manual, but as it's an old motor, and it's been run in salt water, I'm expecting the worst! No doubt I'll be posting back soon if it doesn't come off. Thanks again Steve

achris · Jul 3, 2004

Re: Advice needed on dropping lower unit.

Hey, Post if it DOES come off too. We're all interested.... Chris.

jimalsk · Jul 4, 2004

Re: Advice needed on dropping lower unit.

Steve: After you get this apart and change the water pump take some marine grease and apply it to the spline of the shaft before you put it back together again. This will help prevent the rust from building up. Up here we change the impeller once a season due to all the sand and glacier silt in the water so the shaft really doesn't have a chance to rust up.

steviecops · Jul 4, 2004

Re: Advice needed on dropping lower unit.

I tried removing the nuts and bolts that hold the lower unit on today. They all came out pretty easy, so I thought I might be lucky. I should have known better! The lower unit is stuck on pretty good! I have managed to open up a very small gap at the rear of the unit, about 3/16 of an inch, but the front just doesn't want to seperate. It's almost as if I've missed a screw somewhere. I got the one on top, the one under the cavitation plate, the hex that holds the anode on, and the one under the anode. Are there any more? I haven't tried really belting it yet, as it seems a bit flimsy and I don't want to smash any of the housing! At present, the engine is inverted and I've been trying to squirt some penetrating oil onto the drive shaft somehow in the hope that some will run down to the corroded bit. Don't know how successful this will be. If this motor is anything like my Johnson 55, I'm probably only hitting the impeller housing or inner exhaust with the oil. I've got some wedges and screwdrivers in there, and tomorrow I'll try to open up the crack a bit more. As I said before, I've got plenty of time so I'd prefer to use a softly, softly approach. Still can't help thinking theres another screw somewhere though. Thanks Steve

jimalsk · Jul 4, 2004

Re: Advice needed on dropping lower unit.

Steve you may have forgotten the bolt under the anode plate

Keith Buchanan · Jul 4, 2004

Re: Advice needed on dropping lower unit.

Hi Steve. If there is now a gap you have most certainly got all of the bolts. Regardless of everybody on this post keeping their fingers crossed you have now reached the fun bit. Perseverance ,patience and pressure is the only way you are going to drop that foot, it took me three weeks.. All the best Keith B.. P.S. Steel shims or washers did it for me whilst keeping the drive shaft under expansion..

steviecops · Jul 5, 2004

Re: Advice needed on dropping lower unit.

Thanks for all the advice. Well a bit of a disaster today. I suspended the whole engine upside down, hanging from a rafter in my shed by a rope tied round the lower unit, so the drive shaft/crankshaft connection is taking the full weight of the motor. Anyway, I emptied a can and a half of WD40 into the crack that has opened up, ( there must be a puddle of it around the bottom of the powerhead now!), hoping some of it might hit the drive shaft. Tried more wedges, but nothing happened, so I took the advice of many on here and started beating the crap out of it with a rubber mallet. S**t! I broke a piece off the plate on the exhaust housing. No problem, I thought, that can be fixed later, but I decided enough beating for one day. Next I tried to bang the wedges in further. S**t! I then broke a hole in the side of the lower unit about 2 inches X one! Maybe this can be repaired, maybe not? How can I beat the crap out of this engine when it is so brittle? Every time I try to show the thing whose boss, I break a piece off the engine! As it stands, the engine is still swinging upside down looking like a sputnik with all the screwdrivers and wooden wedges sticking out of it! One tiny, tiny piece of success though. There is now a 1/8th inch gap opened up at the front of the thing, where yesterday it was as tight as duck's ****! If this thing doesn't drop soon, I'm going to take boatsters advice and just cut the drive shaft in half and have it repaired later. Thanks again Steve

Wellcraft 89 · Jul 5, 2004

Re: Advice needed on dropping lower unit.

Forget the wd-40 ,get some PB-Blaster or liquid wrench wd-40 doesn't cut it Rich

Keith Buchanan · Jul 5, 2004

Re: Advice needed on dropping lower unit.

Steve what happened to the softly softly approach?. Oh yes it's certainly character building, you'll learn swear words you never new existed and maybe create a whole load of new ones. Paitience is the keyword it will come. It sounds like when it does come off your local TIG welding guy is going to be busy for a couple of hours..take it a bit at a time, at least for a couple of weeks then throw a Raving Benny.. Keep in there....Keith B....

steviecops · Jul 5, 2004

Re: Advice needed on dropping lower unit.

Kieth, I tried softly, softly and it kept laughing at me ;o) So I hit it a few times! Wellcraft 89, we can't get PB blaster or liquid wrench over here. I've tried something called JB something or other but PlusGas is the one I've had most success with in the past. I'll try some of that.

achris · Jul 5, 2004

Re: Advice needed on dropping lower unit.

Hi Steve, Been reading with dismay at your dilemma. Try a Quicksilver product called Power Tune. It's their de-carbonizer, but it works a treat on frozen bolts/driveshafts. It's good as a cutting fluid too. Good luck and hang in there man. Chris............

steviecops · Jul 7, 2004

Re: Advice needed on dropping lower unit.

Hi Another day, another piece of broken housing! I've spent another day spraying oil, banging wedges, wiggling and jiggling but still no sign of success. Why did Mercury make such a good outboard, with such a lousy drive shaft? The latest news is, I've now drilled two holes in the exhaust housing so that I can see the drive shaft and get a good shot at it with the oil. I've given it a really good soak with PlusGas, (I could actually see it running down the drive shaft), and I've got 6 hard wood wedges banged in as tight as I can get them. The engine is still swinging upside down. I'll leave it to sit and soak over night, then tomorrow, if it still doesn't budge, I'm going to sacrifice the exhaust housing and cut the drive shaft in half. The way it's going, I could carry on as I am for ever, and it still wouldn't come off. The motor hasn't cost me much so far, and the powerhead and lower unit are good, so it'll be worth hanging onto until I can find another one with a blown powerhead or lower unit. I'll keep you posted. Thanks Steve

Advice needed on dropping lower unit.

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