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cswiers
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19 Posts
Discussion Starter #1
OK, 3 prop shafts in 1 year, 2 in the last 3 months. I am running Bravo X drives with Sportmaster Lowers on an F29' CAT. 1.33 gear ratio turning 4 Blade Bravos, 34P props. High X dimension. Stock 496HO motors. Yes has the small prop shafts, but they are sheering off inside the carrier bearing where the shafts are the largest. I saw a mention in another thread of going to after market stonger prop shafts. Anyone had this problem and know the correct fix? Getting expensive leaving a Bravo on the bottom of the river this often, not to mention the shop costs.
 

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cswiers
Joined
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19 Posts
Discussion Starter #3
With 2 in the boat appx 9 to 11 seconds depending on how full on fuel I am. With 4 to 5 on board much slower 15 to 18 seconds. Just takes a while for the 496's to build horsepower, once starting over I have to back down to not blow out the prop's.

No I have not spoke to them, but worth a call.

My boat is a typical DCB, big rooster tail when trimed out, so been keeping the drives a little deaper in the water, but still breaking. I was running straight cruising 80 ish at 4200 RPM's, no load, appx 2 on the trim. So wondering what is causing the stress?
 

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Lord of the Drinks
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2,352 Posts
So wondering what is causing the stress?
The shallow X probably won't hurt you so much unless you are getting the drives out of the water, and not backing off the sticks.

I am by no means a drive expert, but I have been told that torque kills drives...not really horsepower so much. IMHO, you've got 3 things working against you:

1. Firewalling the sticks to climb on plane- that's Torque City.
2. Cruising at 4,200RPMs with tall gears and tall prop is a suburb of Torque City.
3. The Bravo X only has the 1" diameter propshaft (XR has 1.25")

The guys at Max Machine have been down the road to Torque City before, I'm sure they can help you better than I.
 

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It's what we do
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723 Posts
The X has the 1" propshaft. It is not strong enough for a high X dim and 34 pitch props. They can easily be switched to the Mercury 1 1/4" XR propshaft. That will solve your problem.
 

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cswiers
Joined
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19 Posts
Discussion Starter #10
Gentlemen,

Your right..

After a very careful analysis and your input, I am indeed getting bigger shafts.

Hoping for fewer props in the River.

Thanks for your help..
 

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Floatin dirty
Joined
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4,831 Posts
The shallow X probably won't hurt you so much unless you are getting the drives out of the water, and not backing off the sticks.

I am by no means a drive expert, but I have been told that torque kills drives...not really horsepower so much. IMHO, you've got 3 things working against you:

1. Firewalling the sticks to climb on plane- that's Torque City.
2. Cruising at 4,200RPMs with tall gears and tall prop is a suburb of Torque City.
3. The Bravo X only has the 1" diameter propshaft (XR has 1.25")

The guys at Max Machine have been down the road to Torque City before, I'm sure they can help you better than I.

2 very good points here. If those 496's make their max torque output in the 4200rpm range and you cruise for long periods at that range then you could easily be over torquing ans stressing the drives.
 
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