SS930

And IMCO SC drives are frail too, not much better than any of the Merc Bravo offerings since they use the same junk gears. Case stability is an issue, but the real issue is the puny Merc gear set was never intended to support the power, weight, surfacing, and offshore abuse they are being subjected to these days. A few decades ago they were marginally up to the task, definitely not today.

mcprodesign

One note .scx is strong but takes more hp to spin and a 6 needs a tranny . So xr is a cheaper drive that makes your boat run faster . You just have to be friends with a drive guy

kidturbo

So many good points made here we need a short list to help future viewers weigh the best options. Like power to weight, drive height, and proposed operation conditions.

Clearly there is a few of us who've proven they can hold over 800hp / 1000flbs for hundreds of hours without failure. I'm one, who's also torn whether to risk them on a heavier boat that will likely see some air time. Certainly not my first choice. But is it new #6's, or that cute cottage to park the boat at ?

Uncle Dave

Id happily pay you 50% more than the standard bravo gearset for a set of real gears for a bravo.

to the OP even with all the unobtanium parts you can throw at it -- 650Ft lb, in a 28 ft boat w a bravo in the ocean will chew it up like a puppy at the morning newspaper.

to the OP- if Smitty builds it you can trust it.

UD

chewymalone

Amen brother! Every failure I had was related to the vertical shaft twisting in half!

BenPerfected

Our Bravo 30' boat with twin 500 ci NA 750+ HP motors @ 6800 RPM w/650 lbs. has a flat torque curve from 5000-6200 RPM. The torque at 4000 RPM is only 615 lbs. We now have 100 + hours on these drives with virtually no sign of wear. Is the real Bravo killer the big CI motors?...the length/weight of the boat?... or is there more low end torque from 750 HP blower motors? These Bravos do have the best of the best after market parts. Maybe the answer is to not add more CI to make power.

kidturbo

Here was my "technology" fix for the above issues. Won't save ya if you fly out of the water, but she never broke another shaft in the 300hrs I logged.



Being a diesel, major torque is produced below 2000R. This torque limiting map fixed two issues, stiff shifting and the huge torque spike when turbo lit. Once on plane, torque limit was raised to maximum ECU values. Same technique could be used in a gasser to limit the heavy throttle jockeys...

hogie roll

i always check the location to see if the bravo fans are lake boater.

BenPerfected

Hogie,
You are right I am now a lake boater, but the ponds are pretty good size in MI and Nothern OH. Do you generally get some big water in Peoria?
Ben

Smitty

iTrader: (1)

In my testing this is where they break. See the circled areas and follow the red line down the inside of the tooth. The larger line is what you get from a poorly meshing gear.

And don't ask me if I have any to sell yet. It is a work in progress...

All the parts in the drive can/will break if you fly the boat, hammer it, basically drive like an idiot.