ratio change

[Idlespeedonly]

Hi again, just a reminder. I have a 22' ebbtide with a 350 with a bad upper on the outdrive. The current ratio is 21:16. I found a 21:17 unit for sale. I believe this will give me a little more bottom end, which is usually never a bad thing. But how much of a difference would this change make? I really dont want to reprop it, but can if I have to. I am about 400' above see level also. I know the 17's are used on my setup for high altitudes.
Again, thanks for the help.

 

[Don S]

Re: ratio change

I have no clue what you are referring to when you say current ratio is 21:16. That is not even a gear ratio, maybe tooth count on the gears? I have no idea for what you are referring to.
No model number for the drive, no year, nothing to go buy. At this point, I'm not sure you even have a Volvo.

 

[Idlespeedonly]

Re: ratio change

I never said I had a volvo. 21:16 is a ratio, it is also the tooth count. You know if you turn the big gear 21 times the little one will turn 16 times. That is 21 to 16 or 1.313. you have been around long enough to know this. I need advice, not be belittled.

 

[Don S]

Re: ratio change

Well, I meant OMC, I had just come from the Volvo forum.
Fact still remains, there is nothing that says it's OMC or what year, or what drive it is, and 21:16 is not a ratio.
It's also not belittling, it's fact.

PS: Tooth count of 21:16 is a 1.31:1 gear ratio, where the 21 tooth gear turns 1.31 times to the 16 tooth gears 1 turn. that's a ratio as OMC, Merc, or Volvo use it.

 

[Idlespeedonly]

Re: ratio change

It is an omc cause this is the omc forum. 21:16 is a ratio. just not reduced. Like 10:5 is 2:1. kinda like a fraction. The year is an 88. I forgot to mention that.

 

[Lyle29464]

Re: ratio change

6%.

 

[Idlespeedonly]

Re: ratio change

Thank you for the responses. Do you think or from experience know if the difference will cause problems?

 

[Lyle29464]

Re: ratio change

My guess is 250 more RPM. If you were at the middle or low side of of your recommended Max rpm you will be fine. If you were at the max just cool it a bit with the gas.