AQ leg differences 1981 AQ260

[robsboat]

I have a 1981 24' Campion, with an AQ260 package, that has been a project for several years. I found the leg had water contamination in it, and a tear down revealed some corrosion in the double bearing housing that the input shaft/ u-joint assembly passes through. The corrosion is right where the o-ring would normally seat. The double bearing housing uses 2 bolts to attach to the stearing helmet. There is also a small amount of corrosion in the helmet, at the pivot pins.
I also have an older (I think) AQ leg that I tore down to compare for parts, which uses a single bolt to attach to the helmet. I also have the helmet.
Are the parts interchangeable between these 2 legs?
What is the difference between the legs?
All the internal parts have the same part number stamped on them, and they appear the same dimensionally, except how the helmet attaches.
I know I will have to go through the shimming process to swap the parts around.
I have been a truck mechanic for 30 years, so I am confident I can do the work, just not sure about the interchangeability of the parts.

Thanks in advance for any advice, Rob.

 

[RicardoMarine]

Re: AQ leg differences

Rob, the Transmission (aka Upper Unit) interchangeability will depend on which transmission this older AQ series is. There are three driven gear bearing retainer diameters: the 200/250 is small bearing....., the 270, 280, 285, 275, first gen 290, and several more, are the intermediate size bearing....., and the "C" drive and later, are large bearing size.
These will NOT interchange with one another, unless the Intermediate Housing is also changed. So if the bearing retainer diameter is same, then yes, it will interchange with the correct shimming being performed, and with the single screw Helmet being used.
(all lower gear units will interchange with one another when the correct bearing race shimming is done)

NOTE: these gears are provided in sets of three (transmissions) and sets of two (single prop lowers)! We cannot mix/match Hypoid Gears, although I don't think you are asking about this!

In 1981, the Bearing Box was all steel, and the aluminum clamping collar is a separate piece. There will be shims on either side of the "steel collar" of the BB. These shims are also critical as to control gear pattern AND clamping-collar-to-main-gear-case clearance!
These are also prone to leaking water in/around the steel BB, of which you are seeing and have described. These shims may be rusted beyond re-use.
These are considered a wet area if the bolt threads and "collar-to-gear-case" mating surfaces are not sealed well. (there are a few tricks in getting this area sealed well)
Quicksilver Perfect Seal is an excellent product for this!

On a similar note..... I'm finding that most all V-8 transmissions these days are in need of Main Drive Gear Bearings...... ( the bearings in the bearing box. ) These perform a very similar function to that of an automotive differential Pinion gear! (back-to-back tapered roller bearings....., we set rolling torque, gear clearance, etc.) Being a truck mechanic for 30 years, you have no doubt worked on similar!
I would highly encourage you to remove the main drive gear, and examine these two bearings. Simply feeling them may not serve justice..... we need to actually look at them.
They are inexpensive if you buy directly from a bearing supplier. Labor is a bit intensive, but a failure here can be catastrophic.
At least press the gear out, and take a peek!

Also, I would highly encourage you to replace the PDS (primary drive shaft) bearings. (these perform a similar task as does a Gimbal Bearing in a Mercruiser drive) They get over-looked, and typically do not get serviced routinely. A failure here can also be catastrophic.
Again, these are inexpensive if you purchase high quality bearings from a bearing supplier!

Age, related to the eccentric piston seal, can also become a common point of failure. Replace this seal as well. OEM ONLY...., no substitutes!

Rather than typing my fingers off further....., I'm going to link you to a site where I have posted many thread links for help in these areas.


Rob, the AQ series stuff is the Good Stuff. Just do the above, and keep up on the maintenance, and she'll last for another 30 years.

Good luck!

.

 

[robsboat]

Re: AQ leg differences

Thanks for your quick reply, Rick.
My apologies for the wrong terminology, it was late when I typed the message.
The corrosion is in fact in the clamping collar.
I am doing a complete reseal on the leg, with OE seals.
And you are right about the shims, they are toast!
It seemed odd to me that the shims on the clamping collar side are shot, but not on the trans side of the double bearing box.
You are right also about the PDS bearings, no good. My guess is that the bellows failed, allowing water in. I have yet to press the bearings apart in the double bearing housing and examine those. They feel silky smooth, but you are right, better safe than sorry.

Thanks again, I will keep you posted,
Rob.

 

[RicardoMarine]

Re: AQ leg differences

Rob, if you need help, be sure to holler. I don't mind helping one bit!

BTW, that single helmet pin clamping collar can be made to work on the other transmission, if that helps you out.
Shimming for clearance is required.

If you were to remove the main drive gear, pay close attention to the very small shims that will be inside of the main drive seal surface washer. These control bearing pre-load on this particular transmission (later drives use a crush sleeve).
When we change bearings, this shim value changes, as I'm sure you would know.
In fact, when this seal surface washer is changed (and these are often rusted), the shim value changes.
Try to save this washer by polishing the surface to renew it. You can remove .003" - .004" with no issues.
Just an FYI on that!

One more thing; on the lower end of the transmission's vertical shaft will be a brass split ring retainer or keeper..... (aka wear washer).
When these get some hours on them, the shaft up-lift against the split ring, causes this brass ring to expand some.
(if the outer sides are not near perfectly parallel to each other, expansion is occuring)
You don't want this to expand. If so, it's time to replace it.

.