Modern 4 stroke outboards (and perhaps the E tec Evinrude) are certainly a few steps ahead of those a few years ago. I have chosen outboards in a smaller and faster cat--delibertly--and would choose them over sail drives or I/O definately. There are documented reports of 3500 to 7500 hours on medium sized 4 stroke outboards in commercial service. The negitave is less effeciency than a diesel engine, and carrying an explosive fuel. I happen to have two 150 engines, which each charge at 44 amps even at relitatively low RPM, so 88 amps is not bad for a 12 volt power effecient boat--and as much as many single engine trawlers produce. My outboard motors are on Armstrong brackets--which serve as a very good swim step, as well as keeping the engines aft. We spent about 2 years cruising Europe: all of the med and up to the Baltic and back, with 80 hp (diesel inboard) in a 60,000 lb, 46 foot waterline pilothouse motorsailor--for the most part the 80 hp (not much difference between that and 75 hp, except the saildrives have less effecient props)--and the boat's power was sufficient, for all but the most extreme weather. In that case, the waves started to cause damage to the boat, bucking into the seas, so that more hp would not be of much use. I think that with the relitatively small a cat, 75 hp total would be fine in the displacement/low semidisplacement speed ranges. I would think that in steep 8 foot seas, a slow speed cat of 30 feet would be close to its limits of comfortable voyaging. Bob Austin