Gear Ratio- I'm confused??
 

I just disassemble my Bravo 1.... on another thread OSO members were convinced I had 1.36 gears (based on speed & RPM's). However on disassembly I found the pinion is 27 teeth & the drive gear set is 32 teeth. With a calculator this figures to a 1.18 to 1 ratio, but per a gear chart I saw a 27/32 is a 1.5 ratio......??? How can this be mathamatically??
Please explain! :(

Upper and lower combined?

No, this is just the upper housing pinion & gearset 27/32. The lower units on Bravo 1's I thought were all 1:1 ratio, but mine is slightly different from that.... about 1 1/8th turn on vert shaft to 1 turn of the prop..... what ratios are available in B1 lowers??? I'm running 1200 hp in this 31SS Sonic & am not turning but 23" props!! My Formula 312 turns 26" & 28's!! w/454 Mags. Gotta be the gear ratios.

I dont know.

The gears in the lower are 15 driver 19 driven tooth counts. I just counted the teeth on my old gears so I am 100% sure of the tooth count. That should work out but I didn't bother doing the math.

Rene

Ok, that works out to lower drive ratio of 1.27 in the lower.
So, 1.18 upper
1.27 lower

Is that a final drive ratio of 1.5:1????
Come on math whizzes!! Clue me in!!:drink:

1.4986, I gues that's close enough to 1.5

Rene

Your Formula 312 has 1.65 drives unless it was changed from what the factory put in it.

Thanks, Rene.... that is close enough!!

My Formula, per the spec sheet from the factory says 1.5:1 drives...... but this issue is with my Sonic 30SS......
This boat still remains a mystery in some ways!! But I love it. Performance is good enough but the ride is really special.
Here it is.

Here's a link to a chart.

http://www.mtboats.com/outdrivegearratios.html