F225 prop question

[09231960]

I have a Yamaha F225 on an Alumacraft trophy 200,this is a 20ft aluminum open bow boat.The prop that was recommended to me was a 14 3/4"x21 pitch 3 blade stainless.I get a lot of porposing with this prop after just trimming it up a bit.Prop runs out ok but at top rpms I do have a lot of steering torque,hard to steer either direction and I do have hydraulic steering.
Any ideas? Could my motor be mounted to low,it is mounted as low as it can go.

I know I can go with a smaller diameter prop but being that these boats seem to be tested with the larger dia.I would like to stick it.

 

[hwsiii]

Re: F225 prop question

Exactly, what make and model of SS prop do you have. And yes, I would bet anything that your motor is mounted WAYYY too low, creating your steering torque problem.


H

 

[09231960]

Re: F225 prop question

Quickslver mirage

 

[hwsiii]

Re: F225 prop question

You have a raked prop that is trying to lift the bow but can't hold it up or you have a load distribution problem probably. I can help but I need information.

Welcome to Iboats prop forum and we will try to help you as much as we can, but there is certain information that is needed in order to help you. Working over the internet and not being able to see the boat or prop the question is about makes it much harder to propose a solution to the correct prop that you need, and most people don?t know the make and model of the prop . When we get information in bits and pieces we continually have to look back and forth to try and piece the information together. The following form has all of the information that is needed to help you with your problems in finding the right prop. If you do not know all of the information that is asked for on the form please give us the most information you have available as I have a program I designed to find the right prop for any planing hull boat that needs this information. It requires time to find all this information when we have to look for it and in my defense I expect you to be willing to expend as much effort in finding the right prop as I do. We hope to be able to help you get the best prop we can for your particular uses, and this information is required to do that.
It is not as simple to pick the right prop as most people coming to this forum think it is, that is why we ask so many questions, it is for your benefit we ask all these questions. And if you have a stainless steel prop or are changing to one the blade geometry of the prop can make a lot of difference in speed and RPM. Most of my calculations are done assuming an aluminum 3 bladed prop will be used, when changing to a SS prop or changing within SS props we need to discuss what you are trying to accomplish.

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
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
7A If you have a mercruiser and don?t know the ratio get your serial off the outdrive and go here http://www.sterndrives.com/mercruisersterndrives.html
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 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 much higher elevation
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

 

[09231960]

Re: F225 prop question

Screwed up on the prop,it was a quicksilver thunderbolt.
Boat is a 2004 Alumacraft trophy 200,aluminum hull,20 ft long by 8 ft wide,dry weight is approx 2000 lbs.
I can have up to 8 people at a time in the boat but normally have 3-4 people in it,35 gallons of gas.used for fishing 90% of the time.
It is a deep vee but not sure of the dead rise,may be 12-13 degrees.
Motor is a 2004 yamaha f225 4 stroke,225 hp.2 to 1 ratio.
RPM recommendations is 6000 at wot.
Anti-vent plate is 1/2" above bottom of boat,measured at the very bottom of the V.
No tabs or foil.
Some prop info: Right now I have a 14x23 aluminum Michigan wheel vortex prop on now and it runs out at 5600 rpms and approximately 44mph.
I have also tried a 14 1/4 x 21 aluminum pitch that seemed to run up to 6200 rpms.and about the same speed.
The 14 3/4 x 21 pitch thunder bolt ran out at 5500 rpm and about 46 mph on my gps.I had a lot of problems with this prop with porposing so I got rid of it but have struggled ever since.
I have also used an 13 3/4 x 21 pitch yamaha aluminum that I believe ran out at in the high 5000 rpm range and about the same speed.
These other props do handle better but I know I should be getting better performance.
I am at about 1200 ft above sea level.
I do believe my tach is either flawed or I have some sort of a problem with my motor,because my tach has read higher at times but yet the engine sounds the same.
This motor has very few hours on and I did check the plugs this year and they looked good.
I may have to purchase one of the tiny tachs just to make sure.
I am just trying to get the best performance out of this boat.According to Yamaha performance bulletin I should be getting in the low 50 mph range with a larger diameter 21 pitch prop.
Thank you

 

[hwsiii]

Re: F225 prop question

OK, lets do first things first, we have to have reliable tach and GPS speed readings, anything else is a crapshoot. Get a Tiny Tach and even a handheld GPS or some phones have a GPS.
Next we need to look into a zero rake prop with cup on the trailing edge so we can raise the motor up one more hole. The reason we want this prop instead of a high rake prop is you already have a porpoising issue and as you load the boat up with people a high rake prop will NOT be able to hold the bow up, so we are going to pick the stern up instead and that will raise the whole boat out of the water and be able to handle 8 people nicely.
We are not going to get full HP at 6,000 feet elevation, so we need to adjust the prop so we can get 6,000 RPM with at least 3 people in the boat, because you say you run with up to 8 people at times.
So get us some good WOT RPM readings with speed using the Vortex prop and we will use that as our baseline for getting the right prop for your uses and needs.

I run a 16' flats boat with a 40 HP Force at 26 MPH with 4 adults and 3 kids regularly so I understand loading up a boat. LOL

H

 

[09231960]

Re: F225 prop question

The only prop I have a good reading on is the 14 x 23,which i know runs out at 5600 and 44 mph.
We have a cabin that we have to get to by boat,so we always have up to 8 people in the boat to get up there and then of course we use the boat for fishing and normally do not have any more than 3-4 people in it for that.
when i ran the prop out i was by myself.
The 23 pitch does take a bit to get out of the water.
What is the manufacture on the tach you mentioned?

 

[hwsiii]

Re: F225 prop question

The 14 x 23 is the vortex prop and it has too much pitch for even you by yourself much less the loads you carry, it should be realll slow getting out of the hole with 8 people. And you have to make a decision, do you want to be able to go 50 MPH by yourself and have a dog on your hands when you put 8 people on the boat, or do you want to go about 45 MPH no matter how many people are on the boat. They are mutually exclusive of each other, a prop that gets you the fastest speed with 1 person is not going to be able add 8 people and have much performance at all, unless you want to start testing a few 4 blade stainless props until we get the right one, that is your decision.
But, I can tell you something is wrong with the numbers you are giving me, because you are showing a 28% prop slip with you in the boat by yourself and that is ridiculous for a boat with a total allup weight of about 3,100 pounds and a power to weight ratio of 14 pounds per HP. Here are my numbers.

Prop Slip

You need to raise the motor up one hole from where it is now for maximum performance for sure.
After rereading the limitations of the tiny tach I don't believe it is suitable. Get a shop tach or just a handheld tach to check that your tach is working right, But first try and turn the switch on the back two or three times back and forth, beause some of the time they just get a small amount of corrosion that moving the switch can clear up.


H

 

[09231960]

Re: F225 prop question

I will be going back to a 14 1/4 x 21 next time I use the boat,I will also look at getting the motor up a notch.
After that I will get some better numbers using the 21 pitch.
I will let you know.I am looking for all around performance,speed is not that critical at all for me,I have just felt that I should be getting better performance all around out of this rig.

 

[hwsiii]

Re: F225 prop question

I made an error, you need to move the motor up 2 notches, and I believe going back with a 21" is a good idea for the tests.


H

 

[09231960]

Re: F225 prop question

Hello,
what will that do moving it up 2 notches and is there a better aluminum prop I should buy to test with?

 

[hwsiii]

Re: F225 prop question

The aluminum prop you have will be fine, you don't get into real heavy blade geometry until you get a SS prop. Moving the motor up higher will create less drag from the outdrive in the water, and you have 28% prop slip right now and that is high for that light a boat.


H

 

[09231960]

Re: F225 prop question

I did notice you had my elevation at 6000 ft,that is incorrect I am at 1200 ft.

 

[hwsiii]

Re: F225 prop question

Sorry, my fault, it is called CRS. I am also talking with another person who is at 6,000' elevation.


H

 

[09231960]

Re: F225 prop question

ok finally getting back to you on this. I did raise my motor 1 hole,put a used 3 blade stiletto ss 14.25x21p on and took it out,made a big difference raising the motor,I ran it out at 5900 rpms and 49.7 mph (gps).The prop i had was a little nicked up and one blade had a slight bend in it.But i did get a good feel for the differnce it made.
Any other suggestions for props? Would a larger diameter be better or just stick with the 14.25?

Thanks for your help

 

[09231960]

Re: F225 prop question

hwsiii,
Any other suggestions for props on this one,I was told to try a 19 pitch rev4,but since you helped me out with this was wondering what you thought.

Thanks again

 

[hwsiii]

Re: F225 prop question

Go to Ken and talk to him about your idea, he also has an exhange program if you get the wrong prop, and i think it is $ 35. He is Exellent.
http://www.propgods.com/forum/default.aspx?g=topics&f=1


H