Prop Locking Question (Reverse Locking Cam?)

[BB63QM]

Ominous advice, but maybe spot on. At this point, I’m hard pressed to get the carrier out…the puller from Oreilly’s isn’t long enough to straddle the prop shaft and it’s not slipping out like they show in the repair manual and how-to’s online. So if I can’t figure this much out, replacing worn hears maybe above my paygrade. I’ve got a rebuild for $750 sourced. If it was $500, it’s already be here, but I haven’t found that yet.

 

[merc850]

I had a 1975 LU and the bearing carrier was stuck so bad that removing it ruined the housing, if you soak it with the propshaft vertical in penetrating oil for a while it might free up (I just bought a new LU)
Another alternative is buying a complete motor for parts with a good LU.

 

[BB63QM]

Carrier removed without damage (though the gear that was supposed to be attached was not). Problem identified (assuming that the gear fell off during removal)…the clutch dog is swedged on all teeth, front and back, and of course so are the locking grooves in the forward and reverse gears. So, all three need to be replaced. The gear surfaces themselves do not appear to be damaged.

Now struggling with removing the forward gear (ie, removing the pinion gear to gain access to the forward gear). Just a matter of being one person trying to hold the shaft from turning while loosening a nut with nearly no bite with the other hand.

 

[merc850]

Clamp the driveshaft in a vise horizontally then use a box end wrench to undo the pinion bolt, use a rag on the wrench to keep it from damaging the internal threading.
More details:

 

[Chris1956]

Gee, it has been a long time since I worked on that gearcase, but I seem to remember that I could not get the pinon gear off the shaft. I did remove the nut, but that was all I could manage.

I seem to remember that I was able to get the forward gear out, even leaving the pinon gear installed.

 

[BB63QM]

Thank you, both. I’ve been fortunate so far that everything comes apart well (it’s possible that this is not the original LU (there is a slight mismatch in the mating surface at the forward tip), so I don’t think I’m working against 50 years of age and neglect…just 20 or so.

Looks like I’m either going to invest in a table vise or in a drive shaft adaptor nut. We’ll see tomorrow.

 

[BB63QM]

For those that are following along: I found the culprit. It seems that the Clitch slide (30624) snapped (this is the part that sits between the clutch spring and the clutch pin). This led to the sporadic failure to get into gear and getting stuck in reverse, and may or may not have contributed to the worm gears (by jamming the clutch and/or not allowing the sprint to fully eject the clutch and/or by bouncing around in the gearbox)
As for how the steel slide (1/2” shank with 1/4” hole on it for the clutch cross pin) broke? Your guess is as good as mine. Shifting too fast, shifting too slow, bad/dirty lube…or all of the above.
As soon as that part arrives, though, I’m up and running with all new gears, bearings and seals.
By the way: note about the pinion-nut removal: the pinion nut removal tool does not fit (it’s made only for Mercruiser which must be slightly larger than the older Mercury LUs…lt just takes two people (one on the top of the drive shaft, with a 32mm socket and breaker bar and another down at the nut (17mm, also with breaker bar)(or open end 17mm slipped between the shaft/dog and pinion gear…makes it easier to keep the nut isolated)

 

[BB63QM]

HELP!!!

I ordered and received new gears, a new slide, and a new shiftcam, BUT then found that the gearbox in use is NOT the gearbox from and 850 but instead appear to be from the 800, so it looks like some of the parts that I bought will work, but others down match.
760394-Shiftcam—Same
30624-pinSlide-Same
52-822539T-DOG-Same
43-56517T3-FWD-43-75314T2
43-56516T-REV-43-77562T
15–29955A1-Shim-notnoted
12-71143A1-ThrustWasher-12-76358
30-31265-Bearing-not noted
52132T1-Carrier-41529T2

All other parts are the same in both lists except the the 800 doesn’t list (or have) the cup washer (12-29590) or splined washer (12-31211Q03)

Two questions:
1. Why are the gears straight on the 850 and slanted on the 800 (faster, slower, better, worse)?
2. Are the gears interchangeable given that everything else is the same?? After all, I have all new versions of the 850 gears, whereas the dog connections on the existing gears are rather worn.

 

[BB63QM]

HELP!!!

I ordered and received new gears, a new slide, and a new shiftcam, BUT then found that the gearbox in use is NOT the gearbox from and 850 but instead appear to be from the 800 (or later model 70-80-90), so it looks like some of the parts that I bought will work, but others don’t match (including all the gears I busted hump to find here there and everywhere)
760394-Shiftcam—Same
30624-pinSlide-Same
52-822539T-DOG-Same
43-56517T3-FWD-43-75314T2
43-56516T-REV-43-77562T
15–29955A1-Shim-notnoted
12-71143A1-ThrustWasher-12-76358
30-31265-Bearing-not noted
52132T1-Carrier-41529T2

All other parts are the same in both lists except the the 800 doesn’t list (or have) the cup washer (12-29590) or splined washer (12-31211Q03)

Two questions:
1. Why are the gears straight on the 850 and slanted on the 800 (faster, slower, better, worse)?
2. Are the gears interchangeable given that everything else is the same?? After all, I have all new versions of the 850 gears, whereas the dog connections on the existing gears are rather worn.
View attachment 388671

I’m guessing that the gears are interchangeable, but only if I have the matching carrier (the back of the reverse is shaped differently in each version)…otherwise, everything looks to be the same (or the doffeeentlces don’t seem to matter (like the different drive shaft and spring there on in the 850 vs the 800’s LU)

 

[BB63QM]

Also another question: in both versions, the reverse gear does not ride on bearings (as does the forward gear on its tapered bearings)…this seems to be an odd approach, having the reverse gear’s friction only reduced by gear oil, and I suppose balance, as the shaft itself rises 2 sets of bearings outboard of the FWd/Rev gears.
—no matter…just thought that it was weird that the reverse gear not only has no bearings but that it mates up against the littlest/rough back end of the carrier (with all its gear look flutes).

 

[BB63QM]

Also another question: in both versions, the reverse gear does not ride on bearings (as does the forward gear on its tapered bearings)…this seems to be an odd approach, having the reverse gear’s friction only reduced by gear oil, and I suppose balance, as the shaft itself rises 2 sets of bearings outboard of the FWd/Rev gears.
—no matter…just thought that it was weird that the reverse gear not only has no bearings but that it mates up against the littlest/rough back end of the carrier (with all its gear look flutes).

Correction…in the 850 version the reverse gear has a ball-bearing set and corresponding recess in the carrier; in the 800 version, the reverse gear does not, and rests instead against a rough and pitted end of the inner side of the carrier, or a pad of gear oil in the gap between the carrier and the back of the gear, where a spacer and ring lie. Still…seems odd that they put a gear in there that relies on lube rather than bearings for friction reduction (see side-by-side, below):

 

[BB63QM]

HELP!!!

I ordered and received new gears, a new slide, and a new shiftcam, BUT then found that the gearbox in use is NOT the gearbox from and 850 but instead appear to be from the 800 (or later model 70-80-90), so it looks like some of the parts that I bought will work, but others don’t match (including all the gears I busted hump to find here there and everywhere)
760394-Shiftcam—Same
30624-pinSlide-Same
52-822539T-DOG-Same
43-56517T3-FWD-43-75314T2
43-56516T-REV-43-77562T
15–29955A1-Shim-notnoted
12-71143A1-ThrustWasher-12-76358
30-31265-Bearing-not noted
52132T1-Carrier-41529T2

All other parts are the same in both lists except the the 800 doesn’t list (or have) the cup washer (12-29590) or splined washer (12-31211Q03)

Two questions:
1. Why are the gears straight on the 850 and slanted on the 800 (faster, slower, better, worse)?
2. Are the gears interchangeable given that everything else is the same?? After all, I have all new versions of the 850 gears, whereas the dog connections on the existing gears are rather worn.
View attachment 388671

I’m guessing that the gears are interchangeable, but only if I have the matching carrier (the back of the reverse is shaped differently in each version)…otherwise, everything looks to be the same (or the doffeeentlces don’t seem to matter (like the different drive shaft and spring there on in the 850 vs the 800’s LU)

I went ahead and ordered the 850 carrier and bearing, just in case…seems to me to be a more solid design so I’m hoping it is interchangable.

 

[BB63QM]

I went ahead and ordered the 850 carrier and bearing, just in case…seems to me to be a more solid design so I’m hoping it is interchangable.

Can someone please respond to this? The interchangeability seems logical to me, but I am hesitant to go solo on this. My assumption is that so long as all the internals match internally, are cross identified as being appropriate for the model, and fit, then they are interchangable. If not, how does one figure out which LU they have other than by reference to the part numbers of the components (ie, I have not actually seen a part number on the case itself).
In the part lookup, there are two LU cases, each easily distinguished by its skeg shape. The rounded skeg has straight gears and no reverse bearing; the sharp skeg has curved gears and a reverse bearing. Both are interchangeable as a whole. Indeed, as indicated below, BOTH designs have the same part number: (#1655-7333T23)


So does that further mean that the inner parts are also interchangable? Or do I have to get a different (#1655-7333T23) in order to use the curved gears that are spec’s for my (#1655-7333T23).

 

[Chris1956]

I cannot answer your question, however, the older Mercs like your 850 had the gearcase with the rounded skeg (your bottom picture). The sharp skeg didn't come out until the 90's.

I do not expect many here on the forum to know your answer, unfortunately. Rebuilding a gearcase is not a common skill.

 

[BB63QM]

I cannot answer your question, however, the older Mercs like your 850 had the gearcase with the rounded skeg (your bottom picture). The sharp skeg didn't come out until the 90's.

I do not expect many here on the forum to know your answer, unfortunately. Rebuilding a gearcase is not a common skill.

Thanks,Chris. I was hoping blindly that you knew… I’ll stand pat for now…and ask the boat guru at the local shop next time I’m there.
Near as I can tell from the internet, there is no performance difference between straight and curved gears, just a longevity difference (curve gears last longer due to increased surface contact on the teeth….which may not mean much of the weak point in the LU is the dog and dog-mating surfaces).
Or maybe I’ll keep my eyes open for the OEM gearcase, empty and on the cheap, and give it a go.
Thanks.

 

[Chris1956]

You could certainly get a bad gearcase on the cheap (maybe even free) and swap your stuff into it.

 

[Chris1956]

I have a good one from a '77 IL6, here on the Jersey shore. You were in Ca, right?

 

[BB63QM]

You could certainly get a bad gearcase on the cheap (maybe even free) and swap your stuff into it.

This is my current plan (meanwhile, I’ll run on the prior LU with updated dog and slide). If anyone has or knows where I can find mid 70’s IL4 gearcase on the cheap, let me know.

 

[BB63QM]

I have a good one from a '77 IL6, here on the Jersey shore. You were in Ca, right?

I am in CA; my assumption is that the IL6 and IL4 were the same in that era. Can you point me to the part diagram for the unit you have?

 

[BB63QM]

Ok. So after replacing the dog and slide and reinstalling the gears (recall that the replacement gears didn’t match; they were for the oEM lower unit/carrier), we took the boat out Saturday. Started right up. Idled out fine, got up on plane fine, then we slowed down and when we sped up again, it slipped the gear. No fwd, no reverse. From then on, Shifting to N was dead in water and F was limping at like 2 mph (prop either spinning from shaft friction or from the dog attempting but failing to grab the fwd gear. (Recall that the gears were visibly worn before). Made the best out of it and putted around the lake for a while before going home. Sometimes the speed would fall back, then I would shift to N and back to F to get back to 3-5 mph.

Thoughts?

1. Should I try putting the new gears, new carrier, etc in the existing LU
2. Send the new (slant) gears back and get (straight) gears to match what is being replaced.
—and maybe a new dog if it got ground during Saturday’s experiment
Or
3. Give up on DIY and get a pro to look at it, and at least give it a good diagnosis, if not a quick fix to boot.

Something else? Could it be that the carrier wasn’t driven in far enough leaving too much play in the gear?

I’ll crack it open later this week and see what is what inside the gearcase (is anything broken)

Thanks for the advice.