Mirage Plus

[flamingmike]

Hi, I bought a Glastron GT205 2010 (with 4.3L, Alpha and wakeboard tower) and it came with a Mirage Plus 19P prop. I don't know much about propellers and I'd like to understand why this particuliar one was installed. From what I read, it is a very good prop and it's low pitch should make it good for hole shots but worse at top speed. It runs at about 46-47 MPH at WOT 4800 RPM.At this pitch, I read that my engine should overrev but it does not. Is it a side effect of the larger size at 15 1/4 inch or the total weight of boat and equipment? Should I keep it or change it? Although it has a wakeboard tower on it, it`s not my primary use. I rarely go top speed too but usually do 3000-4000 RPM cruising around with familly and friends.

 

[Texasmark]

Usage is not the determining factor on prop selection. The "gear train" needs to be established at max speed and rpm and the prop is the tail of the dog.

Depending on the engine, the manufacturer specifies a suggested wide open throttle (WOT) range and you are advised to be in it with your normal load with the trim setup optimized and the throttle firewalled. If you have done that and are there, leave it alone if you are happy with it otherwise. If your rpms are at a limit of the range or outside of it, then changes would be in order regardless of how you run at partial throttle and you are correct on pitch and effect. Some engines, like my small cubic inch displacement, high rpm 2 stroke (cycle) engines, like to, and have to (really), run at top end of the range. On big block engines it doesn't really matter where you are in the range as you would have the torque to get your horsepower delivered and don't need to keep the rpms up. HP is what turns the prop shaft and HP = (torque x rpm)/5252.