Posts: 433
Location: Cedarburg, Wisconsin | If you are getting 48 I think you are just about maxed out right now. I ran a hot 150 with a kicker on my aluminum 18.5'er and never saw over 46 gps with a normal load of three guys and gear.
If you are serious about getting every last mph out of your rig, you need to get an accurate tach and water pressure gage. Then you need to run WOT at max trim to get the rpm reading. From there you can compare it to the mfg. rpm range suggestions and adjust pitch accordingly. It's a lot of work and when you start playing with props and getting them worked, and playing with the mounting height of the motor, you can expect a lot of time wasted and $$$ out the window. But if money isn't a problem, go for it.
You need to get the motor height right first or you are just chasing your tail so to speak. Plus if you change props the height might have to change again too. Changing pitches won't have the effect it should and you will get very confused all over again. Been there, done that, not fun.
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Posts: 3504
Location: Elk River, Minnesota | Hiya,
Since you are running a Yamaha power plant, I would say a good pro-series propeller would do very well on the rig given the correct pitch. The pro series is designed with high rake and excellent cup, so it stays hooked up, even at higher motor heights. Other props to consider would be Michigan Rapture, Ballistic, and if you can do it, the tempest would be a decent choice as well. Powertech has a bunch of different designs that match many of the other brands as well.
I believe with a good prop and motor height adjustments you can reach that 50mph mark with the boat. It will take a little playing, but the power is there, the adjustablilty is there, and even tweaks on the hull can get you a tad more. Being an alumacraft owner myself and having paid a visit to the factory to work with an engineer on my hull due to a porpoising issue years ago was a great learning experience, but it also gave insight into how one can do some minor things to the trailing edge of the hull that affects how the boat reacts when trimming.
The boat will come with a great tachometer through Teleflex so there will be no need to replace it anytime soon. A water pressure gauge is only needed if you decide to add a jack-plate to the boat in order to raise the motor up beyond the possible bolt locations already designed within the motor itself. Therefore, you will be safe with any mounting height of your motor if you stay within the designed bolt holes.
Being that you have not even taken delivery on this rig yet, being able to get any good read on a prop is going to have to wait until you have completed the break in period. Then, if the dealership you go are going with has a blue-prop demo program, see what different props they will let you take out and test. Different fin designs, venting, diameter and pitch all play important roles in what you decide is best for you. All out speed will sacrifice hole-shot (to some extent...very prop dependent) and usually sacrifices handling as well. Likewise, great handling usually means a sacrifice in top speed. In all, finding the prop that suits your needs is a compromise, but if you get multiple props to work with at the start, one will stick out among the rest in almost all areas. That sets your starting point for tweaking. Definitely there is time involved in this, but if you get into little tweaks and such, it is a fun challenge to take on.
Once your prop is chosen, you can change motor height right in the parking lot at the launch if you choose. all it takes are the right tools and your boat trailer. Doing it for the first time will make you nervous, but once you do it, you will find it is extremely easy to do.
Lots of stuff to think about, so I would take caution in getting too far ahead on things. It is easy to over-think some things which could lead to disappointments. You've got a great rig coming.
Steve
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