Mercruiser drives, whats the difference?
 

I will need to replace at least one of the Bravo three drives on my project boat, a Formula 400ss. Would be looking for something used. After searching around I have not found a good explanation of the different drives, X, XR. Are certain years better? Are the sweptback better? What is different on the "diesel" drives? The engines are mostly stock 502 mpis but I hear these boats are a little hard on drives because they are so heavy. I would rather replace them both with something stronger now if possible.

By the SCXs below then add Whipples :drink:

How many hours are on your motors?
Why does only one drive have issues?

Both motors are being rebuilt now, bored,decked, je pistons, heads rebuilt,mild cam, nothing special close to stock. The drive I need to replace I put on my other boat when the bravo 1 had a pretty complete failure at 2000 hours. (Yes, I actually have three boats. I might have a problem, so what of it, lol) Other boat is a Baja 260, and the bravo 3 works so good on that boat that I'm leaving it on.
At least one of the drives on the Formula has been replaced at some point, they don't match. They have a slightly different style, one has two anodes in the cavitation plate and the other only has one. I have been searching around and am not finding any good info on differences, what years have what changes or witch ones are better.

The strength order is bravo, x, XZ, XR. A 3 is a regular bravo upper with the dual lower. All the way up to XZ is helical cut gears which typically have a longer life. XR is a straight cut which is stronger but the gears wear out faster. Some people have had good luck with the XZ from what I've read. I'm sure others will chime in with more info or make adjustments to this.

You can get a Bravo III standard, X, and XR. 400 SS's eat Bravos, period. The drive with the 2 anodes is a newer drive.

I keep hearing about 400ss being hard on drives that's why I'm trying to find out if any of the stronger drives are worth it. What fails on them? Most of my driving will be just cruising around at 30 mph. Are the "X" and the "diesel" the same thing? I have read that the diese is upgraded to handle more torque, but cannot find specific info.

You can pop drives just cruising. I've seen top caps popped off, vertical shafts sheered, lower gears shucked all cruising down the lake at 40 some MPH. The stress on the drives to plane that boat out is huge. Depending on RPM at 30 MPH, your engines may be at or near their peak torque.

I saw something at LOTO shootout weekend that I found interesting. There was a 400 SS on the dock of the condo I was renting. It had a set of Bravo III's that had a set of Bravo Shop blue decals on them that said something along the lines of Bravo Shop Performance. You could call John at The Bravo Shop and see what he does for Bravo III's on 400 SS's to help them live.

I would make sure you can reach max WOT RPM with the drive, this way your not lugging the motor and torque is kept as low as possible. Also make sure they have drive showers installed.