Logo
FULL SITE MENU

1974 Shifting Inop after Dealer Replaced Seals

7

74merc50

Member
Long story: I sent my 1974 Mercury 50hp to the local dealer (same one the boat was purchased 44 years ago) to have them replace the leaky drive and shift shaft seals. Before sending it in , I had been running the boat weekly and the shifting worked fine, forward, neutral, and reverse.

I get the unit back and I'm preparing to rejoin the foot to the lower unit and I notice that the rotatory shift linkage is very loose. By loose I mean when turning it, there is zero mechanical resistance. Prior to sending it in and all other times I had worked on this to replace water pump impellers, I could easily test the shifting to be sure I was in neutral before joining it to the engine.

Though I told the mechanic to also replace the prop seals, he skipped that saying the they don't leak. The point of replacement was not to fix a leak, but as a long overdue maintenance action. 44 years is a long time for outboard prop seals.

So, I can not get the motor to shift at all, it's always stuck in forward. If I move the shift shaft all the way counter clockwise (CCW), I feel a click that takes a bit of pressure to do and it locks into position. This sets the gear box to neutral. If I turn the shift shaft all the way clockwise (CW), there is a springy feel but requires constant pressure to hold that position. This again sets the gearbox to neutral. No reverse anywhere. For the entire smooth, friction free travel of the shift shaft, the motor is in forward.

This is what I fear has happened:
The shop claimed to be very busy, so they assigned this to some new guy or the janitor. In changing out the prop shaft seal, they pulled the entire shift shaft out of the gear box. As I understand the gear box operation, this would result in unloading the cam follower, extended the spring to full out.
That would make it impossible to reinsert the cam in the proper position. So, instead the mechanic inserted it 180 degrees out of position so he could button it up. I'm guessing that the proper re-assembly would be to pull the prop shaft, position the cam in the proper orientation and then reinsert the prop shaft, properly loading the spring and cam follower.

Does this sound plausible? or am I missing something. I hate to wrench on the shift shaft in hopes of flipping it. One guy over at thehulltruth forum suggested I do just that. I'm not sure, but I don't think the cam can actually spin 360'.

So, if the shop agrees to repair it the RIGHT way, they can provide the new gear lube AND the new seals for the prop shaft, because cracking them open after 44 years will likely create a new leak. https://youtu.be/AgyeUHH_V0g

Any suggestions or advice is welcomed.
 
Last edited:
Nobody know of the proper way to replace that shift shaft seal? Can the cam be removed and put back in without pulling the prop shaft?
Just no other explanation for how this is messed up.
 
racerone said:
Turn shift shaft ccw to get neutral.----Then assemble with control in neutral.-----Common misconceptions here.
Click to expand...

Ok, so where is reverse?
At no point in the travel of the shift shaft does it shift to reverse.

I saw another thread where someone said that if you pull the shift shaft from this type motor, the only way to reassemble properly is by pulling the prop shaft and re-loading the cam / follower. You can't just drop it down the hole in the reverse position and hope it works.
Sound more like misinformation than any misconceptions. I'd love someone to back up these suggestions with technical reasons why.
 
The problem lies in that in Fwd gear, there is always spring tension against the shift cam. So, when the Dunderhead "mechanic" pulled the shift shaft all the way out, the spring-loaded clutch pushed the shift cam out of alignment. It's impossible to just reinsert the shift shaft, as you've observed. Unless you know the "little secret"!

I stole this from a post I made Many Moons ago at the iboats forum, it's for an 850 but your lower unit is built the same way and the solution to the problem the same, as well:

"The shift cam normally pushes against a plunger which pushes on the shift clutch to force the clutch to the Neutral and Reverse positions.

There's also a very stout spring located in the shift clutch assy that pushes the clutch firmly into Fwd gear when the shift shaft cam is in the Fwd position.

There's always a little bit of spring tension pushing on the shift clutch, so you can imagine what happens when you pull the shift shaft up out of the way, "Boing" goes the shift cam in its little cavity.

The only way to do this without disassembly is to relieve the pressure on the shift cam so it can be repositioned and the shift shaft reinserted in the cam's splines.

To do this, grab hold of the driveshaft so it won't move.

Turn the propshaft clockwise (the way it ratchets).

When you are turning the propshaft you'll feel a "click" as the "dogs" on the shift clutch "walk" up the "ramps" of the Fwd gear then fall off them.

The next time it's "just" about ready to fall off the ramp and click again, STOP. You have just relieved spring tension on the shift cam by letting the dogs on the shift clutch "walk" up the ramps and stay there. What this is doing is pushing the clutch to the rear and removing tension on the shift plunger.

So, the shift cam is now free to move about in its little cavity. Unfortunately, the cavity is not so "little" that you'll always see the cam when you look down in the hole. Not to worry, the cam cannot move far enough to be forever lost or fall somewhere, it just slides around a bit.

You may need to jostle the lower unit to and fro to get the cam moving about to where you can see it. Once you can see it, you can align the hole in the shift cam and slide the shift shaft back in place.

To be sure you've got the shift shaft fully inserted into the cam, spin the shaft around and you'll be able to feel if the cam is spinning with it.

Don't worry if, while you're moving around, the propshaft falls off the "ramp", just set it up again. And you'll probably figure this out but, even residual gear oil is thick enough to keep the cam from moving about freely. Spray a little carb cleaner or other solvent or light lubricant to wash away the residual gear oil. Then the cam will rattle around like crazy.

All that's left at that point is to install a new shift bushing. Lube up the threads and O-ring of the bushing with some waterproof grease, or spread on a thin coat of Permatex #3 aviation-type gasket dressing. This serves as a barrier against salt or mineral deposit buildup, which would make the bushing difficult to remove the next time."

Hope that helps. The only other alternative, if you have no success with the above procedure, is to take apart the lower unit, pulling-out the propshaft and realigning the shift rod/cam. And I would force the shop to fix their foul-up, for free, since their irresponsible "repair" work caused the problem in the 1st place!

G'luck with the repairs............ed
 
@Ed-mc - Thank you for that confirmation - I really needed the second opinion before calling the shop this morning. I am 100% sure that their "mechaniac" did what you confirm...he pulled the cam out and the follower popped out, so he just dropped it back down 180 out of position. Wonder what was going through his mind...."oh yeah, it should work this way too". In either method you describe, it will require more shop time ($112/hr), a drain of the gear lube then nickel and dime me another $5.00 "shop fee", $3.95 "environmental disposal" fee, which they charged me last time even though I brought the unit in drained of lube and they just put all the used parts in a plastic baggie and taped it to the unit. This is what I will be demanding, on THEIR nickel of course...
1. Drain the lower unit lube.
2. Remove the prop shaft.
3. Remove the Shift Shaft, reinsert in the correct position.
4. Replace all prop shaft seals, since cracking these 40+ year old seals will likely damage them.
5. Reassemble properly.
6. Fill lube.
All no charge.
Let's see what happens.
Shop is SportOMotive, Appleton, Wisconsin.
 
Back
Top