Drive Ratio and Durability - Any correlation???
 

I have been pondering this and was hoping maybe there were some answers out there.

With the same given torque does drive ratios affect the durability of the drive? Meaning could one expect more, same or less durability from a 1.65 vs 1.36, etc????

Just wondering this as my boat (single vee, 700hp) seems to work fine with a 1.36. Debating switching to a more typical 1.5 and wondering what if any affect that would have on the longevity of the drive (everything else being equal - parts, labor, hours, etc).

I remember back on the alpha drives that were installed behind BBC, they ran 1.36 gears because they were stronger. More meat. I'm unsure if that holds true with the bravo as the top cap is the weakest link, not the gears so much.

Gears not weak in a bravo??? Even on an XR the gears are the weak link.

The closer to 1:1 the stronger the gear set. in an auto diff the pinion gear is larger the higher the gear ratio (lower numerically). 1:36 should be stronger if the pinion gear is larger.

Keep in mind that one of the issues with the bravo gears is the face galling off...not just the strength.

Gears not weak in a bravo??? Even on an XR the gears are the weak link.

The closer to 1:1 the stronger the gear set. in an auto diff the pinion gear is larger the higher the gear ratio (lower numerically). 1:36 should be stronger if the pinion gear is larger.

Keep in mind that one of the issues with the bravo gears is the face galling off...not just the strength.

if u r willing to change your x dimension then the answer is yes. dynamic loading + - is a huge factor in durability. prop blades have a major influence in vibration and the order of. it's all about amplitude and frequency ( xr gears have more than xz's by the way) from the engine to the prop factors into the equation and needs to be assessed as a system and not individual components . installing aftermarket parts are bandaids. just as a #6.

ps. i took a 30% failure rate bravo race team to a ZERO % failure rate.

I had hear that a 1:50 XR upper with a 1:50 lower is stronger or puts less stress on the upper than using a 1:36 lower. I also heard the gears were cut differently. But I do not know this for a fact.

gear ratio is in the lower

only on the XR models

So the the secret is reducing vibration and shock load? Are you saying the xz upper gears have less vibration? As far as adjusting the X...are you saying to go deeper to reduce vibration?

more blades reduce vibration.

proper engine and shaft installation reduces vibration. by the way i wrote a global 8D that was published globally about this.

stand off boxes greatly increase dynamic loading.

zx gears are bevel gears=lower vibration than a straight cut gear like the xr's. the xr are more durable.

you can pop the caps and look at gear wear. if there is a pattern? you can remove the stress riser and flip the gears and run the backside of them.

if anyone is having bravo issues i can come in and asses the system and make recommendations.

the data i have collected on bravo's is extensive. tracking every part in them as well. our race boats have NEVER been out of the water without the drives being rebuilt. if the boat ran for 15 min the drives would come down. some of the smallest cheapest parts can cause a massive failure that will tell you nothing.