Sp to DP??

[steiger23]

Have a 1990 SP-A drive. Is there any DP outdrive that is an easy bolt in replacement? What model, vintage?

 

[bruceb58]

You can bolt on just the lower of a DP-A. I am not familiar with what years go with your drive.

 

[PatinIdaho]

You can bolt on anything from a AQ280-DP to a DP-C1. Make sure it is the correct gear ratio though. The gear ratio changes with the lower unit.
Also make sure you fallow the manual and properly shim the new lower unit to your mid section. Also gear oil changes to a GL5 type
6Cyl. 2.30:1
SB V8 1.95:1
BB V8 and diesel 1.78:1
Also there is a change in the lower unit vertical shaft length by i think 1 inch. Volvo Penta makes 2 couplers 1 short and 1 long for this. You can usually find either one on E-Bay pretty cheap. So you may or may not need a different one.

 

[steiger23]

My SP-A is marked as 1.61. Found a DP lower unit on eBay listed as 1.95:1. Will this work?? Engine is a 305 w/ 2 barrel Rochester.

 

[Maclin]

All DP lowers are the same gear reduction, the final net drive ratio depends on what upper unit ratio you bolt it onto. Bolted to a 1.6 you get a 1.95. So there really is no 1.95 DP lower unit, it will just reduce whatever it is bolted to by its' set ratio.

 

[PatinIdaho]

All DP lowers are the same gear reduction, the final net drive ratio depends on what upper unit ratio you bolt it onto. Bolted to a 1.6 you get a 1.95. So there really is no 1.95 DP lower unit, it will just reduce whatever it is bolted to by its' set ratio.

Wish i could post links to other sites.
This is incorrect. Check marine parts europe and look at all the schematics. On the Transmissions they only list 1 gear set for each Transmissions revision (2).
All the Lower units list 3 different gear sets to obtain the needed gear ratio because the lower unit determines the overall prop shaft gear ratio
With the SP-A Transmission in question there are 3 different lower unit gear ratios you can use as shown listed above depending on application.
For this we want a a lower unit listed as 1.95:1 as thats the proper ratio for a SBC 5.0/5.7 engine

 

[HorizonblueDK]

All DP lowers are the same gear reduction, the final net drive ratio depends on what upper unit ratio you bolt it onto. Bolted to a 1.6 you get a 1.95. So there really is no 1.95 DP lower unit, it will just reduce whatever it is bolted to by its' set ratio.

This is not correct.
On Volvo 270,280,290, SP & DP, there is only one ratio for the upper unit. The overall ratio is determined by the lowerunit, which is stamped into the housing, close to the prop shaft.

When replacing the lowerunit with another one, it is important to obtain the bearing race for the taper bearing on the vertical shaft, which is pressed into the upperunit it is taken off. This bearing race must be installed in your upper unit, with the correct amount of shims under. There is a bearing race in your upperunit, when you remove the lowerunit, yes, but if you just slam another lowerunit on, you mix two different bearings and don't know if there is a correct amount of shims under the bearing race.

The result of this can be premature wear.

 

[Maclin]

This is not correct.
On Volvo 270,280,290, SP & DP, there is only one ratio for the upper unit. The overall ratio is determined by the lowerunit, which is stamped into the housing, close to the prop shaft.

When replacing the lowerunit with another one, it is important to obtain the bearing race for the taper bearing on the vertical shaft, which is pressed into the upperunit it is taken off. This bearing race must be installed in your upper unit, with the correct amount of shims under. There is a bearing race in your upperunit, when you remove the lowerunit, yes, but if you just slam another lowerunit on, you mix two different bearings and don't know if there is a correct amount of shims under the bearing race.

The result of this can be premature wear.

Sorry.

 

[steiger23]

Cannot find any stamping on the lower unit. All I see is the metal tag on the upper unit indicating SP-A and 1.61.

 

[PatinIdaho]

You need to remove the prop and the anode behind the prop. Clean up the bearing carrier and you will find it stamped there it could say 1.61:1 or just 1,61