1988 35hp - Multiple issues

[retroroy]

Last week I answered an ad for a free aluminum boat on CL.
The boat and trailer are great, the motor is a mess, but it came with a spare 'parts' motor.
Both are 1988 35hp Mercury remote control long shaft motors.
The motor that was on the boat runs but doesn't pump water, the 'parts' motor is seized.
Both are premix motors despite having "Oil Injected" written on the face plate.

I've run an older Merc 400 (40hp) for years on another boat so I'm familiar with these in general. The problem is that neither lower unit will drop down.
I have both motors on stands, both have been soaked with all sorts of pentrating oil for a week but no luck. The lower unit on the parts motor drops down about 1/2" but won't come free of the power head. The running motor's lower will only drop about 1/8".
(When I turned the parts motor over on its flywheel on the bench all sorts of small internal bits fell out, several pieces of piston rod, several busted up bolts, and chunks of aluminum and bits of roller bearing cage hit the floor. The bits of rod add up to both rods. The motor though is locked solid, one rod dented the starter motor the other was sticking out next to the carb having punched through both the main block and the intake casting just below the top right bolt.
The motors are both 1988, the boat is a 1989, and the last registration sticker on the boat expired in 3/90. My guess is that whatever happened here happened fairly early in the life time of these motors. They were in a barn covered in tarps and up on a second floor loft.

Any ideas on how to free up a stuck driveshaft?
I'm thinking I may have to resort to cutting one mid, and one driveshaft in hopes to end up with enough parts to make one good motor.

 

[flyingscott]

Either tip the motor on its power head and run penetrating oil down the driveshaft and hope it works. Or take the lower unit apart and remove the pinion nut and drop the lower. This will leave the shaft hanging in the power head yet. May have to break the water pump housing. Then pull the power head and you can get to the top of the shaft.

 

[Chris1956]

Tip the good motor on it's head and suspend it an inch off the ground. If the ground is concrete, pad it. Liberally spray penetrating oil into the 1/8" opening, hoping some will hit the driveshaft and run down into the crankshaft spline. Tap some wooden wedges into the 1/8" opening to add some pressure. Don't crack the midsection or gearcase. Wait and spray......repeat....Tap on the wedges a bit every once in a while to give her some vibration. Say a prayer or two....

 

[racerone]

Drill a hole in skeg.----Use Mercury lifting tool in flywheel.---Anchor motor to a post or tree.---Attach chain to the drilled hole.-----Pull the lower unit off with comealong / chainfall / pickup truck.

 

[mirrocraft16]

Drill a hole in skeg.----Use Mercury lifting tool in flywheel.---Anchor motor to a post or tree.---Attach chain to the drilled hole.-----Pull the lower unit off with comealong / chainfall / pickup truck.

A buddy of mine did something like that, he attached the flywheel to an anchor pot in the shop floor and a chain to the lower unit attached to a chain winch hanging from a gantry crane. He applied a good amount of pressure, soaked it for a day or two, then when nothing moved he kept cranking on the winch. It gave way fairly easy but it broke the pinion gear off in the lower unit.
The driveshaft isn't that big where the pinion splines are.
He ended up cutting the driveshaft off at the crank and trying to drill out the stuck spline end, but it wouldn't give Even after drilling up into the broken stub of the shaft it wouldn't budge. It was as if it were welded.
It went so far as to having to tear down the power head and replace the crank. He ended up trashing the motor and finding another one.
In the end, even after sawing off the stub end of the crank and heating it with a torch, the spline end of the shaft would not come out.
The worst part was that it had been off about 4 years prior with no issues, and he swore he had greased the splines.

I've got an early 70's 4hp here that had the shaft stuck in the crank too, the power head was junk but I needed the lower unit. I literally cut the power head apart to get the lower off, then after cutting the crank down to nothing but the lower 3/4" or so that held the stuck driveshaft, I heated and pounded on it over an anvil only to realize the splines of the driveshaft were completely rusted away. I basically ended up cutting the crank away bit by bit till I got down to just the drive shaft splines.

The idea of flipping the motor over and soaking it through the 1/8" gap may not do much at all. Keep in mind the shaft is shielded by the water pump housing and exhaust tube inside.
If the one motor is junk, maybe a hole into the side of the mid section and then the exhaust tube to get at the shaft with an air hammer and some PB Blaster or Kroil.

 

[Chris1956]

Not sure about the 35HP Mercs, but on the 850, 1150, 1500 and my newer 135HPV6 the exhaust housing is to the rear rear of the driveshaft. If you want to drill a hole in the midsection, drill it toward the front, just behind the shift shaft and it will better expose the driveshaft. I personally would hang it and let the weight and penetrating oil give it a try.....

 

[retroroy]

I put a few hard poly wedges in the gap today and set the power head end in a tub, I poured a mix of atf and acetone inside and finally resorted to trying a pair of hydraulic port-a-power spreaders but no luck. I have no doubt the 5 ton hydraulics can force it apart but I also have no doubt I'll be left with nothing but broken pieces.
The gap is just enough to get the very tip of each spreader in place on both sides, about 3/8" or so.

I'm surprised to find these are both stuck so bad, both motors were bought far from any saltwater and the boat was certainly not the type anyone would use in big water.
Both motors are spot clean, despite one being severely blown up, and the other with a damaged lower unit. Neither shows any signs of spending time in the saltwater.

 

[jimmbo]

Are you certain all the Fasteners are removed? If you are trying to drop the Lower Unit, don't forget about the Bolt under the Trim Tab.

 

[Chris1956]

If you peer into the gap, you should see the waterpump housing, as it sticks up from the gearcase a bit. The driveshaft is in the center of the waterpump housing. The penetrating oil must run down the waterpump housing over the slinger, onto the driveshaft and then down the driveshaft into the spline. It is therefore imperative that the penetrating oil gets sprayed everywhere as a lot of it will just drip into the midsection, and not hit the driveshaft. Try to spray at a down angle.

If you try to fill the midsection with penetrating oil, it will likely get into the exhaust ports and into the cylinders, or simply drain out the exhaust relief ports.

 

[reelfishin]

I don't think you can see much if the open gap is only 3/8" or so, you may see the base of the water pump but getting oil down to the shaft itself from there would take a ton of penetrating oi.
If the 87 35hp is a carry over of the older 350/400 twins, then I believe if you remove the two bolts holding the lower mounts to the side of the mid section, at least one of each two holes goes through into the housing, you should be able to hit the driveshaft through there with some Kroil or whatever penetrating oil you choose.

From past experience though, I've only had luck getting one 'stuck' driveshaft to come free on any old Mercury. Usually they're so rusted into the crank they've become permanently welded.
Forcing the two apart will almost certainly result in a broken lower unit, either the pinion shaft threads will give way, or the casting itself will crack.
Remember its cast aluminum your dealing with.
Usually if placing a wedge to the rear half and backing the two forward most nuts off against a couple of washers doesn't do it, your likely beating a dead horse. Your either going to end up doing a ton of cutting to get the power head and mid off that lower, or your going to be replacing a driveshaft to salvage the lower. If the thing is that corroded up, the chances of 'easily tearing down the lower may be slim as well.

Most that I find in that shape end up donating a few basic bolt on parts, and the rest goes for scrap.

I also seem to recall there being some issues with the later 35hp twins in those years? I seem to remember seeing a bunch of blown power heads on those back in the day.

 

[saltchuckmatt]

I to vote that your wasting your time. When they get that stuck even if you get them out they ruin the crankcase splines.

I've tried about ten and only saved one.

Good luck.

 

[mirrocraft16]

I'll second that vote.
I've had a few dozen or so older Mercury outboards here that just wouldn't budge. I left one 50hp sitting upside down with the lower unbolted and chained to an engine hoist, with the flywheel chained to a bar under the two front legs of the hoist. I soaked it almost daily for months and it never budged. I ended up sawing the thing in half in hopes of salvaging the lower and power head. The driveshaft was rusted solid top to bottom once apart. I had to cut completely through the lower unit and shaft to get it apart.
Once apart, I removed the exhaust tube and the rest of the mid section and worked at getting the shaft out of the crank. It was so rusted in place it wouldn't budge even with heat and hours of banging with a slide hammer. I finally cut it off flush and drilled out the center of the shaft, then slowly dug out the splines with a small chisel.
After getting a new shaft, I soon realized the splines in the crank were too far gone to use.
I parted out the power head, kept the bracket and fixed the lower for a spare. The crank and mid section went for scrap.
Out of all the stuck lower units I've found over the years, most were Mercury or Mariners, and I was only able to successfully separate two of them without sacrificing one part or another.

(On the flip side, I fished a 1962 4hp Merc out of a farm pond a few years ago, it was frozen up and wouldn't turn when it came to the surface, but not 'rusty' or corroded. I pulled the spark plug, flooded it with WD40, then with ATF and let it sit in a bucket of atf and kerosene for a week.
After a little work it broke free. I cleaned up the ignition parts, rebuilt the carb, changed the lower unit oil, and gave it try and it fired up on the 4th pull and ran good.
The lower unit came off without issue. It had been sitting in 25ft water in a PA farm pond for who knows how long. A relative bought the place in the late 1960's, and never touched the pond other than to cut back the growth on one side every few years. There was no telling how long that motor was in there, but I fished it out in 2019, still attached to the remains of an old steel row boat).

 

[QBhoy]

Hi. Did you definitely get all the bolts loose and removed ? There will be 4 in total, I think. One for the trim anode. Another that’s exposed after you’ve removed the trim anode. Then obviously the other two (one each side) further forward that are very visible.

 

[QBhoy]

Are you certain all the Fasteners are removed? If you are trying to drop the Lower Unit, don't forget about the Bolt under the Trim Tab.

Looks like you beat me to it !

 

[retroroy]

All four are removed.

I can see the driveshaft though the four lower mount bolt holes, I sprayed half a can of Aerokroil though those holes to run down the shaft, but it don't seem to be doing anything. I've got four wedges in the open gap and its soaking with penetrating oil. If it don't move by next week, I'll likely cut apart the mid section to get to the top of the shaft area.
Its not looking optimistic though.

 

[retroroy]

I went ahead and drilled two large holes in the mid section.
To my surprise, there's no sign of any corrosion inside.
I cut two 3" holes right next to where the shaft meets the power head.
There's a brass washer at the base of the splines, running penetrating oil down the shaft does nothing, that washer completely deflects it away from the splines. The splines show no sign of rust at all, just clean shiny silver metal, yet they won't budge. I soaked it with a mix of acetone and ATF after warming it up with a propane torch a bit.
I'm not concerned about the mid section or power head at all.
I would like to salvage the lower unit through.
The power head is blown up pretty bad, the flywheel won't turn at all, not even a little, yet I can turn the driveshaft and lower part of the crank a half turn each way. When I do, more bits and small parts fall out of the engine block behind the intake and at the base of the block. Just about everything besides the lower unit, prop and some small parts here and there is junk. What ever happened to this when it failed was a catastrophic failure inside the power head.
If I can't get this to come apart by the weekend via soaking and heating it, I'll likely just saw off the base of the crank and split the splined part off the driveshaft on the bench.

I was very surprised at how thin the mid section was, it took less than a half a minute to hole saw through both sides.

 

[jimmbo]

Threw a Rod, and broke the Crank perhaps

 

[Chris1956]

Was that motor submerged, perhaps? I am not sure how the driveshaft and crank will turn 1/2 way, and the flywheel won't budge. Rusted top bearing and broken crank would seem to be a possibility.

 

[slowleak]

With damage like that it most likely hit the water at high RPM, both pistons suddenly stopping and a filling crankcase is all I can picture that would break the crank and rods all at once. If small parts are falling out of the block, then there's a gaping hole somewhere. I tore apart a 25hp that fell off a transom at wide open throttle. The flywheel was wouldn't turn but was sitting at about a 15° angle off to one side, the lower unit would turn but only a little bit each way, one piston was gone, the lower was stuck at the bottom of the bore.
When I got it apart, the lower unit splines were 'bent', the crank had broken where the top rod attached, and the only recognizable part of either piston was the top of the bottom one, that had been broken off just below the rings.
There was no top cylinder wall remaining, all of the inner structure was smashed to bits, the upper crank had tilted and wedged into the block and the lower part was bound up in about four pounds of shrapnel. About 1/3 of the power head got scraped up off the bench into a coffee can.
The consensus was that the pistons stopped due to water in the bore, one shattered, the other hydro locked, thus letting the weight of the flywheel snap the crank. The rods were unrecognizable, both were completely off the crank and no piece was larger than a 1/2" or so.
The block was so damaged that only the top and bottom bearing areas remained, and the bottom housing was cracked. The starter was pushed aside, both by the flywheel and by the bulge in the case where it attached.

The motor was bone stock and from the mid 80's, it was 22 years old when it happened. It belonged to a guy I fished with on occasion back then.
He ruined a lot of motors, either by dropping them, ove-revving them with the wrong prop, or simply by running the wrong fuel mix, or no oil at all.

 

[retroroy]

I can't say what all happened to this but submerging at high RPM is certainly a possibility, but the motor has no signs of saltwater use or corrosion, just a wrecked power head and stuck lower/driveshaft.
With the holes drilled in the side, I can clearly see there's no corrosion, even where the shaft meets the crank.

Its been soaking in Kroil, PB Blaster, and a homemade mix for a week under tension with both the weight of the motor, the force of the wedges, and a few tries with a porta-power. but its not budging.
I even tried heating the base of the crankshaft but it doesn't move.
The splines are completely buried in the crank.

The next step is likely a trip to the bandsaw. I'll cut the thing off just above the driveshaft, right through the power head, and carefully grind away the bit of crank left on the shaft. I don't foresee saving much else off this.

If I can save the lower unit carb, ignition parts, flywheel, a few nuts and bolts, and what looks like a new prop the rest is likely scrap.