hwsiii
Commander
- Joined
- Jan 25, 2009
- Messages
- 2,639
Kymasabe, I started a posting beause Iboats does not allow you to put pitures in Instant messages and I wanted you to see what is going on with your motor and prop at this time.
In my opinion hanging props an make a lot of differene in the speed and handling of a boat. At this point in time I ran some prop slip analysis on your top speed assuming you have a 2.25:1 gear ratio and sine you didn't tell me what it was I used a 1995 Merury 25 2 stroke motor, please verify this. My numbers show you have a prop slip of anywhere from 36% at 6,000 RPM to 15% at 4,500 RPM, and if I have the gear ratio correct none of these numbers are acceptable. Beause either you are running a prop has too little blade geometry at 6,000 RPM or too muh at 4,500 RPM. My first reommendation is to move the motor up on the transom 1" and see if you pik up some speed, but be sure and add a piece of wood between the top of the transom and the motor as a filler so the motor doesn't kick to the side or off of the transom. You would not believe on how many boats this can add a substantial amount of speed, especially at lower speeds.
Prop Slip
Now about the Rascal prop, from my reading of their literature their props are more comparable to SS high blade geometry props than any other 3 blade aluminum props on the market. They say the props are high rake props with progressive pitch and trialing edge cup. That makes them muh more comparable to SS props than aluminum and that is a very good thing, and it also means that you would normally need to go down in pith so as not to over prop the boat and motor.
But to analyze which one if any might be good for your boat we need to know what your WOT RPM and speed is, and you didn't supply that data. I also don't know if your boat is a flat bottom or a deeper vee as that would make a differene as well. That is why I have the form I do to analyze what pith and blade geometry is best suited for a partiular boat and motor. As a normal course of events I have found that boats that have a lot of prop slip or too muh bow rise can take adavantage of 4 blade propellers to derease prop slip and also pick the boat up higher in the water column, so there is less surface area drag and thus more speed. But the correct 3 blade high geometry prop can do this as well if it has the correct blade geometry for that partiular boat and motor combination, but I have found it easier to use 4 blade props to correct most of these issues beause there is less chance of piking the wrong blade geometry.
If you would like me to try and size a Rascal prop for your boat I will need more information.
H
Kymasabe said:
In my opinion hanging props an make a lot of differene in the speed and handling of a boat. At this point in time I ran some prop slip analysis on your top speed assuming you have a 2.25:1 gear ratio and sine you didn't tell me what it was I used a 1995 Merury 25 2 stroke motor, please verify this. My numbers show you have a prop slip of anywhere from 36% at 6,000 RPM to 15% at 4,500 RPM, and if I have the gear ratio correct none of these numbers are acceptable. Beause either you are running a prop has too little blade geometry at 6,000 RPM or too muh at 4,500 RPM. My first reommendation is to move the motor up on the transom 1" and see if you pik up some speed, but be sure and add a piece of wood between the top of the transom and the motor as a filler so the motor doesn't kick to the side or off of the transom. You would not believe on how many boats this can add a substantial amount of speed, especially at lower speeds.
Prop Slip
Now about the Rascal prop, from my reading of their literature their props are more comparable to SS high blade geometry props than any other 3 blade aluminum props on the market. They say the props are high rake props with progressive pitch and trialing edge cup. That makes them muh more comparable to SS props than aluminum and that is a very good thing, and it also means that you would normally need to go down in pith so as not to over prop the boat and motor.
But to analyze which one if any might be good for your boat we need to know what your WOT RPM and speed is, and you didn't supply that data. I also don't know if your boat is a flat bottom or a deeper vee as that would make a differene as well. That is why I have the form I do to analyze what pith and blade geometry is best suited for a partiular boat and motor. As a normal course of events I have found that boats that have a lot of prop slip or too muh bow rise can take adavantage of 4 blade propellers to derease prop slip and also pick the boat up higher in the water column, so there is less surface area drag and thus more speed. But the correct 3 blade high geometry prop can do this as well if it has the correct blade geometry for that partiular boat and motor combination, but I have found it easier to use 4 blade props to correct most of these issues beause there is less chance of piking the wrong blade geometry.
If you would like me to try and size a Rascal prop for your boat I will need more information.
H