HI I'm Scott New here so bear with me. I just put a 17 ft. 1970 rienell trihull in the water. The poor thing will only do 20 mph. The motor is a70 hp johnson that ran fine on a 15.6 glastron trihull ie 45 mph at 5500 rpm. I checked cable and carb adj. a/ok , anti cav. tabs 1/8 " above keel. Prop is a 13.25x17 piranha. I wonder if the transom angle on the two boats were different. THANKS for any help Scott PS I can't find any reference for the normal weight of this boat. A possibility the boat is water logged. Thanks again