What gearing do I really have

[wellcraft26]

Hi, I have a carolina classic 25 with a 8.1 engine with a volvo penta dp d1 stern drive with b4 props and I'm only turning up to 4200 rpms when trimmed and about 3900 when is not trimmed, the serial number tag show that is a 1.78 gearing, I also remove the anode behind the propellers and I also see 1.78 but there is some engraved numbers in the propeller shafts and I've been told that by reading those number I actually have a 1.68 gearing. I would like to know if you guys can help me with this, the numbers in the propeller shafts are as follow:
3855602 04-021
044
F-12 (R-3) P-3

It looks like if I do have in fact 1.78 I should have a c4 props and that is why I'm trying to find out what my gearing really is as it looks like the gearing could have been changed and everything else, like the tag and housing left as stock.

Thanks for any help in advance.

 

[Scott Danforth]

you should have 1.78:1 with the DP drive

 

[wellcraft26]

you should have 1.78:1 with the DP drive

Going by the serial number tag and the stamping behind the anode in the LU it should be 1.78 but since this person who seems to know Volvo penta units pretty good if make feel a bit worried if I don't have 1.78. I don't want to spend money in a note set of props until I make sure what I have. I have sent several emails but It looks like nobody knows what this numbers mean.

 

[Scott Danforth]

your choices are 2.15 (generally found on 4-bangers) 1.98 (found on V6 and V8's) and the 1.78 (found on the big blocks)

no other gearing available

if you want to check, pull the drive, turn the input shaft 10 times, count the number of times one of the props turns

 

[wellcraft26]

But he is referring if someone during all this time replaced the gearing.

 

[Scott Danforth]

again, if the gears were replaced, you have 3 choices or you must custom hob gears and change gear centers