Re: Not reaching proper rpm or speed
Yea, you can get too high, but if the boat is still accelerating with the RPM gain, you're good. if all you get is, say 5200RPM at 60mph, and you trim a bit farther and get 5300-5400 with no speed gain, but DO gain a roostertail, you are lowering efficiency. The more trim used beyond what results in max fwd speed or max RPM, the more power you have that is un-usable.<br />You want the engine as high as possible that will allow the needed lift with the minumum amount of trim.<br />It may require a higher quality prop to achieve this.<br />The problem you have, is the faster you go, the more lift the stern has because of the hull design, which in turn, requires more positive trim to keep the nose up...The prop is fighting the hook and the hook is fighting the prop <br />
No more huge rooster tail. Ran 23tempest plus and got 53.88 (gps) @ 5100 rpm. The 23 has been worked and has a good bit of cup to raise bow. Hole shot 3 sec with just me and fishin gear.<br /><br />ran 21m yamaha prop and got 51.8 (gps) @ 5500 rpm. Not as much bow lift (as 23) and felt like too much hull in water. Hole shot was 2 sec again with just me and gear. <br /><br />Motor seems to be at right height and both props shot rooster about half as high as top of motor. Both had good acceleration 23 had better. <br />
With this info, you answered your own question as to the affect of efficiency...the roostertail was not an indicator of the perfect set-up, as your speed increase tells us that especially with a lower RPM...Problem is, 5100-5200RPM will kill your engine over a shorter period of time that you may like.<br />You have hull issues that a prop may not fix, but the RPM needs to come up even if the speed doesn't.