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Mercruiser Alpha One Gen 1 Lower Unit Shaft Wear?

R

Royall

Contributing Member
Hi there,

So I had a little water intrusion in the lower unit and after pressure testing it seems my oil seals at the top are broken (shift rod and main shaft). Now after further inspection I noticed my top shaft has movement in it, I also question the sound it makes when rotating. Is this movement acceptable or do I have problems now that require me to change the bearings cause I don't have the tools for that unfortunately...


Hope someone can help :)
 
Pull UP on the shaft when checking for noise.------But if there was water in there I would take the lower drive apart.-----It did not sound promising.
 
lower units without the preload pin work by driving the gears upward when running perfectly normal play Try doing it with the drive upside down ,youll see the difference
The merc tool pulls the shaft upwards to check the backlash
 
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For the record, in my video I demonstrate sidewards movement (Only at 22 seconds I show up/down movement in the video). I am curious if that sidewards movement is okay or that it should be firm like the propshaft is.
 
on that drive the gears force the shaft upwards forcing the bearing on the shaft up and into the race under the wp base
 
Without the shaft pulled up into the bearing cup, there is nothing to stop the shaft from side play. As said above, when running, the pinion gear pushes the shaft up into the tapered bearing just below the water pump.
 
Thanks guys, I turned the drive upside down and noticed that the shaft didn't have movement any longer. I will just try my luck and reseal the unit with new oil seals :)
 
Royall said:
Thanks guys, I turned the drive upside down and noticed that the shaft didn't have movement any longer. I will just try my luck and reseal the unit with new oil seals :)
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How long since the lower bearing carrier had new seals? There's a special tool that allows replacing them without removing the bearing carrier but if it was mine, I would remove that and inspect the O-ring, gears, bearing, etc.

How long have you owned this?
 
jimn said:
How long since the lower bearing carrier had new seals? There's a special tool that allows replacing them without removing the bearing carrier but if it was mine, I would remove that and inspect the O-ring, gears, bearing, etc.

How long have you owned this?
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I've bought the boat 3 years ago. I don't know when the previous owners changed it.

I was under the impression I could just use 2 drywall screws to pull them out (prop shaft seals).
 
Royall said:
I've bought the boat 3 years ago. I don't know when the previous owners changed it.

I was under the impression I could just use 2 drywall screws to pull them out (prop shaft seals).
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Where did you get that idea? Drywall screws are usually very hard- removing the seals alone doesn't give you a chance to check the condition of anything else and as the buyer of a boat that was insanely badly main....I'm not even going to say it was maintained because it was just neglected.

If the impeller is two years old- that's often the lifetime of that part, depending on the manufacturer.

The manual isn't terribly expensive and the correct specialty tools can be bought used, so it's not terribly difficult to go through it without spending a ton of money.

BTW- if you check auto parts stores, you'll find that many sell direct equivalents to Mercruiser parts. I bought a seal for the upper gearcase assembly (it's all on the short yoke) at O'Reilley and it was $13- the Mercruiser part is anywhere from $17 to $70, depending on the seller and age- I don't want rubber parts that have had too many birthdays. Seals are seals, bearings are bearings (assuming they're a correct match).

Also, my bearings in the upper are toast and there's no way I'm buying Mercruiser parts when they're actually Timken- mine has 386a bearing and 382a cone (race)- I'm buying branded as Timken, not an equivalent- I trust Timken and traded e-mails with them, so I'm more confident in them than a knockoff, which Amazon has been selling as Milwaukee Electric Tools and others.
 
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