Jim; My guess is that your prop is under pitched.
My 38 will cruise at hull speed (about 7.3 knots) in flat water at 2500 RPM. I have a 36HP Universal M35B diesel with 1.76 reduction gear and a 16x10 1/2 two blade prop. Max RPM on my engine is 3000 RPM, and recommended cruising is at 80% of max, so about 2400. Many of the early 38s were built with an A4 as a standard engine. The A4 had no reduction gear, so it turned the prop at a relatively high RPM and used a prop with a relatively low pitch, something like 7 or 8 inches IIRC. Is it possible that the previous owner converted to diesel but did not change the prop for some reason? You haven't said what prop you have (it may well be stamped on the hub of the prop), nor what the reduction if the transmission is. Some of use would also like to know your hull number and where you will be keeping the boat. There are probably 10 or 12 of us on the list with 38-1s or 38-2s, and maybe double that number with 38 LFs. In case you didn't know it, most prop manufacturers have a spot on their website where you can fill in the particulars of your boat (engine HP and max RPM, reduction, boat length and displacement, etc) and they will recommend the optimum prop size. Surprisingly it will vary from manufacturer to manufacturer, because of slight differences in things like blade shape. But in most cases the recommendation is intended to get the boat to around hull speed at 80% of max engine RPM. Hope this helps. Rick Brass Imzadi -1976 C&C 38 mk1 (HIN 047) la Belle Aurore -1975 C&C 25 mk1 Washington, NC -----Original Message----- From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Jim Lynch Sent: Saturday, March 15, 2014 12:54 PM To: cnc-list@cnc-list.com Subject: Stus-List Prop adjustments and cruising speeds I'm the happy new owner of an old 38-2, and I'm wondering if there is something wrong with my propeller or its pitch. It's a fixed three-blade on a Westerbeke 27 four-cylinder diesel. At 3,000 RPMs it only pushes the boat along at 6.0 knots. Seems like too much exertion for too little return, doesn't it? The engine is strong, the bottom is freshly painted and the boat is not carrying much extra weight. With a hull speed over 7 knots, shouldn't it be chugging along at 6.5 knots or more at 2,500 RPMs? I'd really appreciate any insights from owners of old 38s, as well as those of you who've seen the benefits of prop changes and pitch adjustments for both powering and sailing. Thanks, Jim Lynch Olympia, WA 38-2 --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
