1977 FBC Repower
From what I have been told it would be best to go to 1 1/2" shafts when you go from a low torque higher speed gas engine to a higher torque lower speed diesel. Aside from buying new shafts and stuffing boxes or dripless packing setups (you will almost certainly have to buy new props.. mine are 21"D by 23"P 3 blades and I have the 315/330HP Cummins 6Bs with 1.5 to 1 transmissions). You probably won't have to replace your struts because the 1 3/8" cutless bearings should have enough rubber in them that you can have them bored out to 1 1/2".. or perhaps you could buy 1 1/2" cutless bearings that will fit in your struts. You mention 300 HP Cummins engines.. I believe the next lower HP in the 6 cylinder 6B model is the 240/250 HP version, which while less expensive do not have enough HP to get optimum performance with the B33 hull. My boat came from the factory with Cat 3208s (the previous owner repowered 10 years ago to the existing 6Bs), and some others here still have them, but these are 260 HP and being V8 diesels they weigh about 800 lbs each more than the 6B engines. Granted they are heavier than the 6B configuration with about the same HP, and that certainly effects boat speed, but I think most of us agree if we had our choice we would want to put at least 600 HP into the B33 hull. You can tell from reading posts in this forum the Cummins 6B 315/330 HP engines seem to be the best fit all around with enough power to satisfy most of us. Especially when you consider you can buy the 6B engines as factory rebuilt fully warranteed engines at very attractive prices. With boats.. all it takes is $$$$$$$$! Frank B - IRGuy@aol.com "Phoenix" 1983 FBC Wilmington, NC
Frank B - IRGuy@aol.com "Phoenix" 1983 FBC Cummins 6Bs - 315HP Wilmington, NC