Bob asks: << How much power do I need to move a 46 foot lwl hull at full displacement speed (assumed 9 knots ???). My library was a victim of Rita. As much as I like the old 4/53's, I am looking at a repower. the Hull is a typical early Krogen design (will share the emails from Jimmy Krogen sometime) and would like to have some thoughts from the list. I am looking at a pair of Perkins Prima fifties. Any thoughts ? thanks>> Your hull speed is indeed 9 knots as you assumed. If your boat has a 40,000 lb. displacement and the hull is clean, it should take 57 hp to reach that speed. I know this sounds low for a relatively big trawler but displacement hulls slide through the water easily at or below hull speed. The power required scales up directly as the displacement so if your boat is heavier it will take proportionally more power. The estimate assumes a 50% efficient propeller, probably a bit higher than the norm for most trawlers. I would increase this power by 50% to take care of bad weather and the eventual hull fouling. Don't make the mistake of slapping in a couple of 200 hp diesels. It will just cost you a lot of money and aggravation. There is hardly any circumstance where more than 100 hp would be required. I trust that you will not be towing a string of barges or trying to power into 60 knot headwinds. Larry Z