Offshoreonly.com - Bravo 1 behind 750hp?

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- Drives and Lower Units (https://www.offshoreonly.com/forums/drives-lower-units-217/)

- - Bravo 1 behind 750hp? (https://www.offshoreonly.com/forums/drives-lower-units/320283-bravo-1-behind-750hp.html)

I've read a bunch of theories here and other places on what cause some of these to fail behind 525's, while guys like myself push them far beyond rate hp specs without issue. My personal theory is aluminum fatigue over long time, allowing case flexing to higher clearances. Or too much air time on heavy boats.

Has anyone else ever wore out a SS XR prop hub before the drive? To where you thought the shaft was bent causing prop wobble.

God knows I was never easy on my XR. Multiple groundings, logs strikes, even wrapped a steel cable up and stalled the engine at cruising speed once. But with over 350hrs on the meter, reliability speaks for itself.

Some personal GoPro examples at 330hrs right here:

http://youtu.be/Dhk4eA-Qmgs?list=UUW...mldgz7bXn_xcgg

Well from 8 pages of reading I've gathered it WILL break. Just when depends on how lucky you are.

Quote:

Originally Posted by La/stryker (Post 4236955)

I have replaced the same gear again, exactly the same break. It's like the boat goes into neutral. Reverse still works afterwards its only fwd gear floor.

That's exactly what our's (handful of boats - minimum of a few times each) did and probably a billion other bravo drive owners.

These forums where lit up for years with people doing the same thing.

Now not as much, but more people now-adays have better drives (min of XR's and of course tons of aftermarket) than stock regular Bravo merc stuff. I said more.
I don't know how the people on this thread have kept there stock drives together.

Quote:

Originally Posted by La/stryker (Post 4236955)

I'm having a slightly different bravo 1 failure. I have a 2001 htm ss 24 carbon top cap with the original 565 na motor 650hp with 1050 Dom carb. Had it for two seasons with no problems on river and lake calm water(about 10hrs a year) bravo 1 upper imco sc lower never had chips on magnets just some very minor fuzz. Motor had been freshened before I bought it but no changes. I had to replace the heads because the started leaking small amounts of water thru the jackets and into the cylinders. It was not head gaskets or leaking headers I checked that first. with the new heads smaller comb chambers not sure what the compression ratio is now but getting 200psi plus or minus 10 psi and some cylinders have minor water damage cause heads would leak just sitting in garage. I'm not sure what the current hp is but picked up a solid 2mph, Guessing 675hp
After head change I broke the floor out of the upper fwd gear planing out but it was with about 3/4 throttle takeoff. 30 pitch 4 blade brave prop 1.5 gears. I had it fixed and lasted about 10hrs till next summer when I went to pass another boat I went full throttle at about 4000rpm and about 70mph around 80 mph it broke the floor again and almost over revved, glad my hand was on the throttle! I have replaced the same gear again, exactly the same break. It's like the boat goes into neutral. Reverse still works afterwards its only fwd gear floor. Now I'm scared to run it had cause its a long trip to the boat ramp in reverse if I can't find a tow. Am I missing something? Anyone else had this problem? Boat runs 102 GPS btw and still never had anything but fuzz on magnets and broken gear teeth look fine, no visible sign of wear. Wtf so many people running more power with heavier boats with better luck!

Get a left hand prop if you running a right hand. Then reverse will get u back to the dock going forward. Not a fix for the problem but will help out getting home.

Think I'm just going to replace the upper with an imco scx and keep the sc lower. But wondering how much speed I will lose spinning those bigger gears. Although I will have piece of mind knowing it won't break as soon as I find 10k laying around.
FYI I also have a pair of Gibson slip on mufflers which I don't actually need where I live but have run them before. Boat is a lot more quiet but it will NOT run over 98gps with the mufflers on. 102 with out. They seem to be robbing a lot of power!

Gibson slip ons for sale!!!!

You won't loose anything going with the scx uppers and the sc lowers , I did it.

Quote:

Originally Posted by La/stryker (Post 4237379)

Ok now that we've beat this topic to death got another question. My boat was kinda hard getting on plane last year with the 28p. The performance shop has every kind of prop you can ask for within reason. I can try as many as I want for free. They want me to try a 30 or 31 to start next season. My question is what about going to a 5 blade prop? From what I gather it is harder on your drive but you can get on plane faster. What's everyone's experience between 4 and 5 blades? What do you lose and or gain going to a 5 blade from 4
Blade.

I didnt see much diff getting on plane, but mine doesn't take much to get up,2800-3000 it will pop up on plan,

i would think it would help you though, but unless you went up in power going larger/pitch prop would hurt getting on plane,

I went from 30p 4blade to 28p 5 blade and it dropped/lost about 300rpm