Where do I find out what options are available to replace my DP-C 1,78:1 Sterndrive

I have a broken gear in my lower unit. Have an opportunity to pick up a replacement but the numbers are different. DP-D1
In the bottom: 3102151035
In the top right: 3868022

My unit is DP-C
on the bottom 3102134416
top right: 872776

I'm assuming this isnt compatible. Does anyone know where I could find out which drive options O have? engine is a 7.4litre 454 big block gas.

Your DP-C1 is within the AQ series family.
It will be of Main Suspension Fork/Pivot Tube geometry.... The Good Stuff ! (not a Gimbal suspension drive)

All AQ series Duo Prop lower units can be made to work with all of the AQ series Intermediate housings.
There will be a vertical shaft tappered roller bearing that will need to be re-shimmed.
See the work shop manual for instructions regarding taking the A and B dimensions and adjusting the shim value.

Try to get the bearing race that was originally with the lower unit that you will be buying.
(most sellers do not even think about providing this race with a lower gear unit)

Your DP-C has a short vertical shaft, which means that the vertical shaft coupler will need to be the long one.
(you should already have the long coupler)

Your 7.4L engine requires the 1.78:1 reduction. The 1.78 has a stronger gear set due to the greater tooth contact at any given time.
This is an Over-All reduction that includes the sum of both transmission and lower gear unit.

The DP-D1 is a diesel drive, and will have a different style exhaust outlet on the housing.
I don't know the pros/cons of this for a 7.4L engine.

If you remove the ring anode, you can wire brush the face of the carrier unit and expose a few numbers.
The ratio will be stamped into the carrier, and will/should be correct IF no one has changed the gear set and failed to re-stamp the carrier.




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Icegal20, I failed to ask you if you will be replacing the entire drive, or just the DP lower unit!

If just the lower unit, note that these drives share gear oil between the lower and upper.
The lower gear unit pumps cooler gear oil up the to transmission (for an exchange and cooling) where it then drains back to the lower.
Point being..... if you have contaminated gear oil (due to lower unit gear failure), it's likely that it has gone through the entire system.

If so, you will want to flush the transmission (upper gear unit) out.





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