Please Read !! Prop Help !!

[OneLuv1979]

OK guys i have a 1999 Key Largo 17' with a 1999 90hp 2stroke ...
My issue is the RPM's ...

WOT all i can reach is 4500 with the motor trimmed down , with the motor timmed up i can get it up to 4700rpms trimmed up thats with a couple people in it , but i have noticed it dont do much better rpm wise with just 1 person ....4800rpm

Thinking i might need to switch to a smaller prop ....
Im currently running a Ballistic stainless 19 i have been told by someone who i dont know how reliable they are that i should step down to a 17 as a 19 is to big for a 90hp

My boat currently performs pretty damn well , but i think only reaching 45-4800 rpm's tops is over proped .....
I can break plain around 3200rpms , and WOT Trimmed up @ 47-4800 rpm's im clocking 47mph with just me on it .....

Can a smaller prop get a better speed and be better for my motor , or should i just leave it alone .....

I have also heard that having breather holes cut into the back of the prop could possible help .... Im sure someone can shed some light on what i should be doing ....

 

[hwsiii]

Re: Please Read !! Prop Help !!

One, welcome to Iboats prop forum and we will try to help you as much as we 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, if you would prefer to not go to this much trouble there are other people who will help you.

Iboats Boat and Motor Info
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 recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make and model of motor
7. 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 and turn the motor until the tape lines up with each other, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. 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. If you do not have a tach you can buy a Tiny Tach for $ 50
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the forgoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. 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

REMEMBER, The numbers I give you will be NO better than the information you give me

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