Question about gear ratio

[renken86]

Just looking for help. Right now my outdrive gear ratio is like 21 and 19 with inboard v6. I was wondering if the gear ratio 21 and 13 would hold up? I can get a upper unit with the ratio 21 and 13 very cheap with perfect gears but if they won't hold up then there is no use for it. Any help?

 

[jerryjerry05]

Any idea what year the new gear box is from?
Always include the year, model and serial numbers
on the motor and what ever your working with???
Need the year for better answers.

 

[renken86]

Any idea what year the new gear box is from?
Always include the year, model and serial numbers
on the motor and what ever your working with???
Need the year for better answers.

This is an early OMC Stringer upper gear unit 1968-71 with 21:13 gear ratio used with 80 and 90 HP. He said that it came off a 4 cylinder. Its the whole upper housing. Sorry thats all the info I have gotten.

 

[southkogs]

In '68-'71 the four cylinders used a 16:20 upper and a 19:20 upper. I don't have a 21:13 in my manuals, but I do show a 21:16. Are you sure of the ratio?

 

[kenny nunez]

The pre 73 OMC high profile 4 & V6 and 120- 155 HP used the same drive. Is your boat built before 73? Most 73 on are low profile and are 4” shorter. The 80-90 models were early to 60s and the lower gear housings were the small electric shift outboard units.
Can you post a picture of your drive and boat.
Another clue is all OMC engines were painted gray before 73, then all other stringer models were painted light blue until the Cobra series.