Thanks to Malcolm for his response. I have no experience with power cats. I have been looking at a number of logs (all U S boats) and many run one engine at a time. Some stated that they did this to save fuel. I even have found some outboard run power cats which also do this at lower speeds. I assume that Dennis had fully feathering props, to elimiate the prop drag. 20% increase in effeciency is a lot--and much more than I would expect just from freewheeling a prop (I always had folding or fully feathering props on my racing sailboats. but on cruising boats allowed the prop to free wheel up until the boat speed was 3 to 4 knots , at which time I locked the prop down. My impression was at low speeds that the prop drag was relitatively small in comparision to hull friction, and wave resistance at high speeds, when cruising). I also examined the Yamaha 4HJ3 TE's fuel curves--which are on line. at 2000 RPM it appears that they are burning about a U S gallon an hour and have substantial torque. The engine appears to be producing about 14 HP. (by formula I would expect 20 hp at a gallon an hour). It seems like 14 hp would get these boats over 5 knots. (assuming prop effeciency--and that is what Dennis achieved with the CCP) So one would have to assume that internal friction of the engine and the fuel to overcome this is less than the drag of a fixed prop at low speeds? Most examples of the PDQ were going from 5.5 to 6 knots. Also I wonder what the effect of running both engines at low speeds is over time? Is there a problem keeping the engines up to temperature? Is there a problem with turbo carbon? So is it better for the engines to run one harder--that is with temp up and tubo spooling adequately than to run them at idle? Also, it appears that the Yanmars which are highly turboed seem to be replaced at relitatively low hours when used in the Picnic boats. This combined with a comment by a well known engine mechanic/dealer that he felt that the life expectancy of highly turboed engines was in the neighborhood of 2500 hours, would make me ask the question if it is because of longivity issues that it is preferable to run these engines one at a time? I certainly would agree that the feathering/controlable pitched props are not cost effective for the average user. However a pyrometer is a relitatively cheap instruement and might well be advisable. Malcolm--does your experince of running boats on twins as a preference to single on passages, relate to monohulls also? My experience was that I needed only 150 RPM on a single over twins to achieve hull speed on a semidisplacment trawler. Looking at fuel curves for those engines, it was clear to me that the single was more effecient. Regards, Bob Austin