what 280 lowerunit ratio do I have ?

[ffleury]

I have a 270 outdrive with a 280 lower unit . The engine is a AQ260 V8 . The 280 case casing was damaged and I am looking for a solution . As I am looking to replace the lower unit ( 280) , I had read that all lower unit were the same but I don't know if thsi si true since people talk about different gear ratio and I am assuming that there are mutiple gear ration. May the casing is the same and there different gear in there.

The only marking I could find on the ring behind the Zinc is " V I8". I also removed the shaft and can see 31 teeth on the horizontal shaft and 20 on the vertical shaft . That would give a ratio of 1.55 to 1 which is not the ratio that I could read in any post . I am confused about what I have and what I need to look for .

Thank you for any help
Franck

 

[Don S]

Re: what 280 lowerunit ratio do I have ?

I had read that all lower unit were the same but I don't know if thsi si true

You must have been reading Mercruiser threads or the wrong Volvo drives. The ratio changes in the lower on a 280.

For a V8 engine, you need a lower unit with 1.61 gears.

 

[jerryjerry05]

Re: what 280 lowerunit ratio do I have ?

(I have a 270 outdrive with a 280 lower unit . The engine is a AQ260 V8 .)
AQ 260 must use the 1.61: 1 over-all ratio.


(The 280 case casing was damaged and I am looking for a solution . As I am looking to replace the lower unit ( 280) , I had read that all lower unit were the same )
True for some of the Merc drives, but not with the AQ series Volvo Penta.... with exception to the diesel engine DP "E" drive.

(but I don't know if thsi si true since people talk about different gear ratio and I am assuming that there are mutiple gear ration. May the casing is the same and there different gear in there.)
Yes, the gear case is the same, but the lower unit gears are different for each engine group.
Except for the E drive, all transmission reduction is the same.


(The only marking I could find on the ring behind the Zinc is " V I8". )
Look ahead of the anode on the prop shaft bearing carrier. The ratio should be stamped into the carrier. No matter what you find, the AQ 260 requires the 1.61:1

(I also removed the shaft and can see 31 teeth on the horizontal shaft and 20 on the vertical shaft . That would give a ratio of 1.55 to 1 which is not the ratio that I could read in any post . I am confused about what I have and what I need to look for .)
This is a final drive ratio. In other words it includes the transmission reduction and the lower unit reduction. The sum of both.

By the time that you purchase a 1.6:1 lower gear set, bearings/seals, and perform the set-up, you may as well buy a good used 1.61: lower unit.
Re-shimming above the vertical shaft bearing race must be done.

 

[ffleury]

Re: what 280 lowerunit ratio do I have ?

thank you both. Now i understand that I need to find a new 280 lower unit with a 1.61:1 ratio.