VP gearbox question

[snowbird30ds]

Probably one for Volvopaul here, My gearboxes are plated up as MS4 5 1.95 p/n 356000 on starboard side and MS4 A 1.93 p/n 853398 on port, I can find the port number on the drawings at marinepartseurope but not the starboard number, why would they be a different ratio (albeit only slightly, my props are the same) and why the different part number.
They are contra-rotating but I assume that is just down to the cable orientation.
I have always seemed to use more fuel on the port engine.
I have no problems with them and they are not about to get changed just curious.

 

[petem]

What boat? Are they the original gearboxes? Have you had the boat from new?

 

[snowbird30ds]

I believe the boat originally had tmd40's in and the engines were from a corvette, the engine serial numbers are pretty close together but don't know if gearboxes were swapped at the same time.

 

[volvopaul]

Probably one for Volvopaul here, My gearboxes are plated up as MS4 5 1.95 p/n 356000 on starboard side and MS4 A 1.93 p/n 853398 on port, I can find the port number on the drawings at marinepartseurope but not the starboard number, why would they be a different ratio (albeit only slightly, my props are the same) and why the different part number.
They are contra-rotating but I assume that is just down to the cable orientation.
I have always seemed to use more fuel on the port engine.
I have no problems with them and they are not about to get changed just curious.

Ms4/5 has slightly better gear set with coarser teeth so ratio alters slightly but not enough to alter performance.

 

[snowbird30ds]

Thanks Paul, so was there an age difference between the boxes or just a model change?
S/n's are 3101025869 for ms4/a and 3101108637 for ms4/5 if it helps.
Both hold pretty much the same rpm at wot within 50rpm which could easily be bearing drag or alignment difference.