From Powderpro's 34 CB build
Seatrail numbers, 34 CB
Here are some pictures and performance #'s.
2,000 rpms: 26 mph 13.7 gph
2,200 rpms: 28 mph 16.2 gph
2,400 rpms: 30 mph 19.1 gph
WOT 2,650 rpms: 33mph 25.2 gph
At 2,600 rpms (redline) load is 93%.
These numbers are with a light boat and 6 people on board. Add about 1,000 pounds for a full tank of fuel and another 1,500 to 1,800 pounds of gear, equipment, etc. I would still expect the boat at 2,800 pounds heavier to do 29-30 mph. When the boat does get heavier, I may need to take an inch or two out of the pitch. Current prop is 26x28, 1.75:1 reduction, 500 hp QSC Cummins
Definitely a home run, although I'm not surprised with how light the boat is, how flat the stern is, and how much power the engine produces. That 8.3 Cummins has some serious power. I don't know what the weight of the boat is, but my dad and I were guessing around 14,500 pounds at sea trial. When loaded with fuel, gear, etc, probably about 17,500 pounds. I wish I knew what the weight was, but I don't know. What I do know is the boat jumps out of the water when you give it throttle.
One thing that is different on my boat than most other CB 34's is where we placed the motor. Calvin Beal Jr. suggested a 12'6" shaft length. I'm assuming most, if not all CB 34's have about that long of a shaft. I placed my engine farther aft with a total shaft length of 9'10". So my shaft is 2'8" (32") shorter than what is probably typical. I'm not saying that necessarily helped my numbers, but it may have. My dad and I believe in keeping weight out of the bow of the boat, and the engine is the heaviest single item in the boat, besides the fuel.
The CB 34 called SEACOCK participates in some of the lobster boat races. I think he told me that his engine produces around 540 hp, he has the same reduction as me (1.75:1) and the same or similar shaft length as mine does. He runs a 3 blade prop (mine is 4 blade) and I think he tops out at about 37-38 mph. His boat probably weighs about what mine does, but my cabin is taller and grabs a little more air.
This post edited by powderpro 10:13 PM 07/05/2010
FWIW,
Bill D