Aquamatic Series Drives Compatibility?

[jeffnick]

My boat is a 1972 but there were obvious upgrades done before I bought her. She originally had a Chrysler Super Bee, but the boat came to me with a VP 260A (SBC). Her outdrive is what appears to be a 250. When I bought her I was worried about the outdrive so I bought a running 250 as a spare ($80), but it was for a 4 cyl, not the 8 cyl that I have in the boat.

Well, then I knocked off the anti-ventilation plates on both sides of the outdrive while backing the boat into the boat-port in the back yard. I was thinking that getting the parts welded back on at a machine shop would be at least a hundred bucks so I bought a complete running 280 for a V8 for $100 thinking I'd just use the bottom section...which I assumed I could install on my 250 unit with the proper bearing shim procedure.

In the meantime, I glassed the broken parts back on to the old Aquamatic 250 and because we seldom go above displacement speeds (8mph) I'm convinced we'll be ok.

So now the question.
The 280 is in relatively good condition...clean oil, smooth U joints, no missing parts - everything functional. First off, is it really a 280?

Second - would there be any advantage to using the 280 instead of the 250?

And lastly - what complications could I expect, if any, in case I do replace the 250 with the complete 280?

 

[RicardoMarine]

If you have a good 280 of the correct over-all ratio for your engine, I would certainly use it in lieu of the 250 drive.
It will mate up to the 250 transom shield.
Drive shaft bellowsand exhaust bellows between the two are the same.
All else will connect up.
The exhaust outlet can be retro fit with a 290 flapper, allowing you to eliminate the exhaust bellows flapper (if V-8, I'd do this).

I would most definitely perform a leak-down test on it first (gear oil removed for the test).
I can just about guarantee you that the eccentric piston seal is in need of replacement.
You will not know about the main drive gear seal or the prop shaft seals until you do the leak-down test.
There will be a few Do's/Don'ts for this work......., so don't be afraid to ask questions before attempting disassembly.
Disassembly of the main drive gear clamping collar cap screws gets people into deep trouble if not done correctly!!!!!

Either drive requires 30W or 40W engine oil.... depending on water temperature.... ( I.E., 30W if in cold water.... 40W if in warm Florida water)

 

[RicardoMarine]

Jeff, I failed to answer your questions directly.
Let me take another stab at them.

So now the question.
The 280 is in relatively good condition... clean oil, smooth U joints, no missing parts - everything functional. First off, is it really a 280?
Yes, from all that I can see, it is indeed a 280!

Second - would there be any advantage to using the 280 instead of the 250?
IMO....Yes!
the 250 offers:
anti-rotation pin inserts in suspension fork.... (IMO, this weakens the fork some)
smaller main drive gear male yoke splined shaft (I've not seen many that have become twisted, but they will occasionally)
small driven gear bearings (not a huge issue)
lower gear set is bevel cut... as apposed a Hypoid gear cut with the 270 and later (you'll hear the bevel cut gears more so)
will not accept the long propeller hub nor the larg blade propellers
no decent gear oil fill port that is easy to use
exhaust outlet provides the torque tab/trim fin (not nearly as effective as the 280 torque tab/trim fin)
dip stick and drain plug use a gasket instead of an O-ring.
the collar steering fork shaft diameter is much smaller than the 280, causing the bushings to wear out sooner.
the helmet pin threads are smaller.... although some early 280s also used this pin.


And lastly - what complications could I expect, if any, in case I do replace the 250 with the complete 280?
All will hang from/to your existing 250 transom shield.

NOTES:

When installing an AQ series drive, remove the transmission from the Intermmediate housing first.
Do NOT drive against the hinge pins with anything harder than an Italian Bread Stick.
Heat the aluminum hinge pin bosses as to expand the aluminum some.
Use a brass or aluminum punch on the hinge pins.

Now hang the suspension fork and lower unit as an assembly.
Connect the S hose and install the shift cable and cable clamp.
Raise the drive, and fight the exhaust bellows. (make a wire harness to help pull the AFT end of the bellows onto the Intermmediate housing snout)
Now install the transmission last (you'll need new O-rings)

Trust me on this one...... it will be much easier this way.


NOTE:
A FWD shift will always involve a shift cable "extension" at the drive's gear yoke.
A REV shift will "retract" the cable.
People get this reversed occasionally!

 

[jeffnick]

Thanks Ricardo. Great info!
I did R&R the 250 as a one piece unit to have it resealed when I got the boat. It was a pain - especially getting the drive splines together. I'll know to separate the transmission next time. My hinge pins came out easily...the mechanical stuff on the boat was pretty well looked after when I got it - in fact the motor only had 10 hours on it (probably due to the leaking fuel tanks)?

I notice that some helmet pins have two bolts. My 250 is a single allen. Will this be a problem if I use the 250 helmet on the 280?

 

[RicardoMarine]

I notice that some helmet pins have two bolts. My 250 is a single allen. Will this be a problem if I use the 250 helmet on the 280?

Take the 250 helmet pin and see if it fits correctly in the thread insert of the 280 bearing box clamping collar.
I'm fairly certain that it will!
If not, use the 280 helmet pin.


.