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280 gear ratio

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dabid_miff

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The 280 outdrive got water in

The 280 outdrive got water in the oil from years of storage. It is junk. I have a different upper gear box and a lower unit which sounds like it needs new bearings. I also have a 280 outdrive from the flywheel to the prop. This came off a V8. My boat has a AQ 140 A (4-cylinder) for power.
My question is: Where is the gearing different on the two outdrive units?
How do you check the condition of the bearings between the flywheel and the driveshaft?
Do I have enough parts to rebuild a 4-cylinder outdrive?
 
"David, It is just oposite of

"David, It is just oposite of the early Mercruiser drives.

All V/P AQ series transmissions will interchange if within the correct group...... small bearing 250 for a 250....., larger bearing 280 for a 270 or 280, and so on (for example) and are of the same ratio.

All lowers will physically bolt up, however, the over-all gear ratio change occurs in the lower unit..... Not the upper!
Your ratio will be 2.15:1
The V-8 will be 1.61:1
Again, all uppers are of the same ratio and can interchange within the same group (has to do with bearing size and the machined surface in the Int housing).

If is not cost effective to change out lower unit gears/bearings.......
The set-up time and parts will out weight the cost of a very good used unit.
And there are just too many good 2.15:1 lower units available.... and they rarely ever break.

I have some 2.15:1's here that I can sell very very cheaply if interested, as there just isn't any supply/demand market on these. Best I can get for one re-sealed, is about $475...... I'd sell one for much less. There just isn't any demand since they just don't break under 4 cylinder horse power.

The bearing you are asking about is the Primary Drive Shaft bearing.
There is NO good method for checking this bearing while the shaft is still installed in the Flywheel Cover. Not unless it is so far damaged that side to side movement can be felt by hand.
IMO, it is foolish to NOT replace this if questionable.... a failure here will cause unbelieveable damage.

If lucky, you can remove the seal and the two large expansion type snap rings and remove the PDS from AFT.
You need a special long needle nose snap ring plyers for this.
I just did two of them on the same boat, and was very lucky that they came out easily.
The bearing itself is cheap.......
I can get you a high grade bearing p/n..... cost is about $16, seal is about $6."
 
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