From: "East Cape Marine Ltd" <tech@nzboatbuilders.com> Hello David, Sounds like what they call "Porpoising" Without seeing all the details on the actual design: I am only able to offer a place for you to start looking for the potential problems, in any catamaran set-up. 1. Check to see if the LCB and LCG are too far apart in the design. (If possible) They should be no further than 75 - 100mm Maximum distance between the two at any speed and trim. The closer the better. 2. Weight, such as driver, tanks and other gear could be moved to see if the attitude of the vessel changes at different speeds and trim. This will have effects on moving the LCB closer, or further away, from the LCG. ( start by adding weight aft, or removing weight forward.) 3. Asymmetric hulls with air vents may have an adverse effect on a design under 26 feet if the weight in the vessel is set-up incorrectly. 4. Once the above is cured, try a jack plate for the engine. This is by no way an opinion or criticism on the actual design of the catamaran in question. All the best, Noah Thompson Director / Designer East Cape Marine Ltd. Design / CNC Facility: Unit 4 / 5 Reynolds Place Papamoa Beach Tauranga 3118 Mail: Po Box 705 Te Puke New Zealand 3153 Phone: +64 7 542 5175 Fax: +64 7 542 5176 Mobile: 021 11 00 984 info@eastcapemarine.com www.eastcapemarine.com ----- Original Message ----- From: "david walker" <dwalker434@earthlink.net> To: <power-catamaran@lists.samurai.com> Sent: Friday, 25 May 2007 4:01 Subject: [SPAM] [PCW] 20' cat >I just bought a new 20' single engine (150 e-tec) tunnel-hull >catamaran and have had nothing but surprises. I will not mention the >name hoping I get some resolution of the problems. This is my first >catamaran.