Re: Another prop question - boat is slow...I think.
Ez, welcome to Iboats prop forum and I will try to help you as much as I can but without more information no one can help you, and I will tell you I need more information than anyone else. But if you would like my help fill this form out and I will help you as much as I can.
You might try reading this for a better understanding of changing props for better performance, and for the major differences between aluminum props and stainless steel.
http://forums.iboats.com/showthread.php?t=369057
I also show your recommended max RPM to be 5,500 and your gear ratio to be 1.93:1,
please verify this. If this is true I show your prop slip is over 37% and just changing prop pitch will NOT take care of your problem.
If you would prefer to not go to this much trouble there are many other people who will come along and gladly help you.
1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the maximum recommended HP for your boat
3. Number of people and gallons of gas normally on boat and what do you use the boat for
4. Year, make. manufacturer and model of motor and recommended Wide Open Throttle (WOT) range
5.
HP and gear ratio of motor IMPORTANT
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape across the prop and the lower unit and then cut it between the prop and the housing then do the same thing on the flywheel and turn the motor until the tape lines up with each other on the prop, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
6. Anti-ventilation Plate height above keel of boat if it is an outboard in inches, use a straight edge under the keel and sticking out to the anti ventilation plate for a reference
Motor Transom Height
7. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. Make sure you trim the prop up until it starts ventilating and then just trim in until it quits ventilating.
RPM _________ Speed ______ GPS ______ No. of people ______ Gal. Gas ________
8. Make, model, diameter, pitch, number of blades and whether SS or aluminum prop and does it have a hydrafoil, dolefin or trim tabs
9. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way by just pushing the throttle at the helm and not at the carburetor, checked compression, and looked at the plugs and checked spark as well as timing and advance, all of the foregoing could be the reason your prop is not attaining full RPM
10. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations and does the prop show any damage that you can see
REMEMBER, The numbers I give you will be NO better than the information you give me. I use a computer program I designed to find the correct pitch and then knowledge to pick a Better prop design for your boat.
The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.
H
