I have an 8' little racing type boat with a skiff bottom.<br /><br />A brand new 30HP Tohatsu (4stroker) was installed according to factory manual.<br /><br />Full RPM range is 5,250-6,250RPM<br /><br />A group 24 battery and a smaller 3 gallon fuel tank are strapped down in the rear of the boat behind the seat.<br /><br />Boat hull is easily lifted by two people off a jetski like trailer and is estimated at ~500 pounds.<br /><br />PROBLEM: At full throttle the stern burries down and RPM reaches 3,100 where no more power is given (prop cavitates?). Boat does not jump up onto a plane. It burries pretty good (to the cowling).<br /><br />Full down tilt brings the prop shaft basically on a horizontal plane with the boats hull when eyeballed on a trailer.<br /><br />I am perplexed as this is just about the same reaction I got from the boat on a 9.9HP 2 stroker without extra battery.<br /><br />I have placed another group 24 in the bow and while it flattens the hull for low speed, it has no effect on achieving a plane or getting past 3,100 RPM at full throttle.<br /><br />The engine linkages were checked and operate fine along the full range. Idle warmup lever can get the engine at 6,000RPM easily.<br /><br />Is this a pitch-up or pitch-down on the prop type fix or perhaps some major surgery on the transom to get some rake angle in it to let the engine push the bow down as it power up (at which point I might as well just axe the hull and get a small boston whaler hull).
