Michael and Jerry,
The redline on a over the highway C-12 is 2,100 RPMs under power. The marine version of the same engine has a redline of 2,300 RPMs. The issue here is what is the redline when descending a hill with the Jake brake on, and as much as I have researched this issue, I have never found the answer in any Caterpillar documents. I discussed this subject with an Allison engineer once and he told me that the deceleration redline that they had from Cat for their transmission programing purposes was 2,500 RPMs for RV use, but he did not have access to that Cat information at the time to show me. So at this time, everyone will just have to use the RPM redline that they are comfortable with when operating their coach.
Remember, if you try to research this issue yourself, there are 5 different common applications that the C-12 is used in with the marine, stationary (generators and pumps) and heavy equipment versions being the only ones still in production. The over the road engines that ended production in 2004 are broken down into 2 categories, trucks and RV/firetruck. The Truck engines deliver less horsepower and may have a tighter redline restrictions than the RV and firetruck version because the truck engine is expected to deliver over a 1,000,000 miles before overhaul, but the RV version rarely ever sees 1/3 to 1/5 of that. Therefore Cat is able to turn up the horsepower ratings, but no where near the water to water cooled marine version that can hit 700 HP.
Gerald