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Aquamatic Transmission

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jeffnick

Regular Contributor
Trying to help a friend doing a transmission swap on an Aquamatic 250.
Ta.jpg
Several questions:
The white one (coming out) has posts sticking out of the top. The donor trans doesn't. Will this be a problem?
Are there shims that we need to worry about?
Is it a big deal to replace the transmission seal for the universal shaft?
He has a V8 (white trans) - the replacement is from a 4 cyl outdrive. Is this OK?
Where can I send him to buy/download a manual?
Yes - he has new 125017 and 925259 O-rings.
 
jeffnick said:
Trying to help a friend doing a transmission swap on an Aquamatic 250.
View attachment 22858

Several questions:
The white one (coming out) has posts sticking out of the top. The donor trans doesn't. Will this be a problem?
At one time, those may have been for a bracket used for steering a kicker engine.
If you don't need them, no issues.

Are there shims that we need to worry about?
Yes! See below.

Is it a big deal to replace the transmission seal for the universal shaft?
The main drive gear bearing box assembly will need to be removed.
Before you attempt to remove the 4 clamping collar bolts, use propane torch heat on the main case at the areas of the thread inserts.
The heat will expand the inserts and will help break up any corrosion.
If you were to round out the hex sockets, you will be taking it to a machinist for Milling Machine work.

The 250 main drive gear seal is unique.


He has a V8 (white trans) - the replacement is from a 4 cyl outdrive. Is this OK?
Yes, all transmissions in the 250, 270, 280 series are of the same reduction.
The lower gear unit determines the over-all reduction.
V-8............ 1.61:1
inline 6....... 1.89:1
inline 4....... 2.14:1


Where can I send him to buy/download a manual?
I just found one..... https://sellfy.com/p/NumX/
Steer clear of the Seloc and Clymers manuals.

Yes - he has new 125017 and 925259 O-rings.
The O-ring for the bearing retainer is 925259
The oil drain back tube O-ring is 125017
The shims are 941823, 941824, 941825

The OEM shimming procedure can be rather confusing.
Here's my suggestion that will render the same exact goal:

.......with O-rings NOT yet installed, toss a few extra shims into the shim landing.
.......fit transmission and just snug up the fasteners. Snug them only.... DO NOT fully tighten!
.......take a series of feeler gauge readings around the perimeter between the gear case and the Intermediate housing.
.......jot this value down.
.......remove transmission.
.......reduce the shim pack value by an amount that will now give you a .003" clearance reading when just snugged up again.
.......test/check again to verify.
.......remove transmission.
.......place O-rings onto their respective areas.
.......re-install transmission and fully tighten all four fasteners.
.......the gap/clearance should now be ZERO, allowing for a .003" squeeze of the bearing retainer.
Click to expand...

NOTE:
The 250 transmission uses what we call the "small driven gear bearings".... of which are the double row ball angular contact bearings.... one at the top (under the top cover) and one that will be exposed at the bottom.

The 250 Intermediate housing will accept the small bearing only.

Check to make sure that the replacement transmission is a small bearing unit.

Keep in mind that the cone clutch assembly is designed to work with either 30W engine oil (cold water) or 40W engine oil (in warm waters.... Florida for example).
DO NOT use heavy gear oil!
 
Just to be clear...... you will be "over-shimming" only to determine the gap between the transmission and the Intermediate housing when the bolts are just snugged down.

Once that gap is known, you will reduce the shim pack by an amount that now gives you a .003" gap when just snugged down again.

Once the transmission has been fully tightened down (O-rings in place), the gap will become ZERO, leaving a .003" squeeze that will prevent the outer bearing race from slipping or spinning within it's bore.


.
 
RicardoMarine said:
Just to be clear...... you will be "over-shimming" only to determine the gap between the transmission and the Intermediate housing when the bolts are just snugged down.

Once that gap is known, you will reduce the shim pack by an amount that now gives you a .003" gap when just snugged down again.

Once the transmission has been fully tightened down (O-rings in place), the gap will become ZERO, leaving a .003" squeeze that will prevent the outer bearing race from slipping or spinning within it's bore.


.
Click to expand...

Roger that!
 
So, things didn't go smoothly. Rick warned me...the transmission we were going to replace is a 270 and the donor is a 250 = different bearings. So I'll need to order a seal kit for the 270 to replace the drive seal rather than doing a swap. Do I need to take the top of the transmission off to do the drive seal, or can I get the drive shaft out by just removing the clamp ring. I guess I might as well replace the eccentric seal while I'm taking things apart? The factory workshop manual came today.
 
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