Paul,
I have the BD exhaust brake on my 94' and the first year it was installed I only had the original valve springs(35 lbs. )installed. After a year of use, I came upon a great deal for the 60 pound springs, so I installed them at that time, and have been more than pleased with the performance of this brake system. I too pull a large boat (25 ft cruiser) and can't imagine not having an exhaust brake!
wayne