TOPIC: resurrecting a '73 650 3 cyl

I just bought a Custom Craft that has a '73 Merc 650 on it - working on bringing her back up to speed. I'm a little skeptical of Merc having had bad experience in the past, but this one has been good thus far. I'm not an outboard expert but I'm not afraid of turning wrenches.

When I got it, the powerhead was locked up and the lower is stuck in gear - I got the powerhead freed up, cleaned carbs a bit, cleaned up the starter and she fired right up.

The lower is giving me trouble - I've opened it up, and the shift linkage appears to operate freely, but the ratcheting clutch is seized to the shaft, and I can't get the driveshaft out of the housing so I can pull the prop shaft out and clean it up.

Is there some secret to removing the drive shaft? I have the lower stripped to the point I can see the upper bearing, and it will rise maybe 3/8" up out of the seat, but that's it.

A few pictures. I am thinking the driveshaft needs replacement, or can I run it with the pitting?

You need to remove the nut that you see to the right in the last photo in order to remove the drive shaft.

Melanie

Oceans2 wrote:

You need to remove the nut that you see to the right in the last photo in order to remove the drive shaft.

Melanie

Once I remove the nut, I assume the gear can be dropped out and removed though the prop housing? Seems easy enough.

Correct!

Gotta love a gal who wrenches and knows her way around in a gearcase!

JJ, I don't think the pitting on the shaft is an issue as long as the sealing surfaces (shiny areas on the shaft) are intact. Pits or a groove worn in the shaft in those areas are trouble, as I understand it.

Mark, I checked out all the sealing surfaces and everything is in good shape - I was just concerned that the corrosion on the shaft might be a strength issue - I wouldn't use an axle in a car with that kind of pitting, but as I say I'm no expert on outboards so I figured I'd ask someone who knows more than I

I think that prop shaft is stuck into the forward gear. I do not think (at least on the l4 and l6 merc gear foots) you need to remove the pinion gear nut to pull the prop shaft. You do in order to get the gear out of the nose cone but that prop shaft should just pull out. I think something else is holding it in there. I just looked at the parts diagram and like the l4 and l6 mercs the end of that prop shaft only sets into the bearing within the gear so I think you have some corrosion holding it in there.
Secure the gear casing, put the prop nut on the prop shaft with a plate or something under it to grab onto and with a slide hammer and some heat see if you can persuade the prop shaft out of there.
I never liked these 3 cylinder mercs. L4 and L6 all the way.
So save some sanity you may want to find a working lower unit for the L3.

Could someone tell me why the pinion nut has to come off to get the driveshaft out? I like Jim am confused by that statement. I have yet to work on one of these 3 cyl lower units but all my Inline 4's and 6's pull right out like Jim says.

Is the prop shaft pressed on to the front gear? Does the clutch dog need a bit more clearance to get past the nut?

Conrad

g3jim wrote:

I think that prop shaft is stuck into the forward gear. I do not think (at least on the l4 and l6 merc gear foots) you need to remove the pinion gear nut to pull the prop shaft.

I had intended to pull the gear out of the nose cone anyway to inspect the bearing, buuuut - I am 99% sure at this point that this lower had water in it, because there was a pretty nasty buildup of corrosion on the reverse gear and the shaft (which did clean off nicely).

That said, I imagine that if the shaft should just pull out of the gear (which makes sense now that I look at the diagram again) that it's seized. Pretty much everything has been, so no surprise there. I sprayed it down with penetrating oil last night, I'll see what happens when I put a little hammer-time into it tonight.

Give it one last try. maybe find another lower unit of dump it for parts. I am only 20 min south of Portsmouth maybe we can hook up and have some boat talk.

g3jim wrote:

Give it one last try. maybe find another lower unit of dump it for parts. I am only 20 min south of Portsmouth maybe we can hook up and have some boat talk.

I have been shopping around a little bit, short shaft lowers are pricey (as in more than I paid for the boat!). If I can get it all apart, it shouldn't be too much trouble for me to repair it as long as the case and the shafts are salvageable.

I'm about 30 mins north, but I boat right here in Great Bay usually - if it doesn't snow this weekend I might be tossing my other classic ('73 whaler 13 sport) in for a shakedown / tuneup cruise.

The

---

PROPSHAFT ----should pull out without having to take the pinion nut off.

---

My bet is the propshaft is seized in the bearing on the forward gear.

---

" get a bigger hammer " ---some would say.

"Is there some secret to removing the drive shaft? I have the lower stripped to the point I can see the upper bearing, and it will rise maybe 3/8" up out of the seat, but that's it."

That is the question that I responded to. Not whether it was neccessary to extract the prop shaft, which as a couple people have pointed out it does not. For the record due to a badly damaged skeg on the 115 that came with the Skagit 20 I spent an entire Saturday recently with the master, DR. Frankenmerc, transferring the inner workings of my LU into a good housing he had on hand. Always the perfectionist he wasn't happy with how it felt after the new water pump assembly was installed. I lost count of the number of times we completely disassembled and reassembled the LU but enough times I feel confident I can tackle the LU on my '68 1000 that I think needs seals.

Mark,in the past I was an ASE master tech,shop manager in the automotive field. Although I have have not renewed my certification in several years I still can read a manual and turn a wrench and prefer doing my own repairs whenever possible.

My approach would be to remove the drive shaft and yes you do need to remove the pinion nut to do so,then remove prop shaft with seized forward gear as an assembly to be able to press it off or make it easier use a bigger hammer.Afterall if the shaft is seized to the forward gear bearing would you not need to remove the pinion gear to remove the gear in order to replace the bearing and dress the shaft surface?

Melanie

Thanks Melanie!

I read one thing and wrote another! Geesh... Driveshaft-propshaft-driveshaft-propshaft-driveshaft-propshaft.

Ok now I got it straight.

One note tho, Isnt it a bit tight in there getting that nut off the pinion with the propshaft still in the way? Ya need a socket on a breaker or a double end box wrench to get on that little bugger. I wasnt sure if the Pinion would fall down past the clutch dog and out or not.?

Thanks
Conrad

Conrad

milkdud wrote:One note tho, Isnt it a bit tight in there getting that nut off the pinion with the propshaft still in the way? Ya need a socket on a breaker or a double end box wrench to get on that little bugger. I wasnt sure if the Pinion would fall down past the clutch dog and out or not.?[/quote]

In about an hour I'm going to attempt to answer this question. Hopefully, hilarity does not ensue.

Yes it is a tight fit. Dr. Frankenmerc had ground down both sides of a box end wrench to accomplish the task. He was a wealth of information.

Edit: As I recall it wasn't terrible tight. Thom had a socket that fit the splines of the upper drive shaft. I kept pressure on the nut while he worked the socket. Seeing how your drive shaft is a little on the rough side in the one area pictured you might try using a monkey wrench or large channellock to twist the shaft while holding the pinion nut. Be sure to dress any burrs that result so as not to damage any seal that must pass by.

Melanie

Verdict:
It is possible to remove the driveshaft pinion nut with the cluth and prop shaft still in place, and the gear comes out pretty easily. I used a regular 5/8" wrench on the nut, and found a 17mm is almost a perfect fit to hold the flat where the impeller sits. I did have to use a little "persuasion" to get the driveshaft free from the pinion, and I had to use ALOT of persuasion to get the forward gear free of the prop shaft.

The good news is, the gears and bearings look to be in usable shape, except the bearing on the reverse gear - it's got a lot of rust on the balls and I haven't been able to separate it yet.

Bad news is I found a small crack (1/8" length) at the very aft edge of the lower housing - it doesn't affect any of the threads that hold it together, only the boss where the prop sits. I am thinking corrosion will make that worse if I use it like that?


forward

reverse


Some pitting on the shift cam, but looks usable. All that other black gunk is rust and PB Blaster

Upper bearing looks pretty much new


**edit** I just noticed that I have my Mercury parts spread out on a GM Goodwrench paper mat ... that's ironic, eh ?