Your boats performance is determined in large by what prop you have..
We often get emails asking "What is the best prop for my boat?"
The "correct" prop for your boat is the prop that allows your engine to reach its
factory rated wide-open-throttle RPM's.
Wide Open Throttle is abbreviated WOT.
When we say WOT we mean that you have your boat at full speed with the throttle fully advanced.
Full Speed is the maximum speed your boat go as it is set up.
Testing
Do not buy a prop until you have properly tested your boat with a known prop.
Taking the time to properly test your boat will allow you to get the correct prop.
Before you test your boat, check the following:
1. Engine Performance. Is your engine tuned and running strong?
2. Hull condition. Is the hull clean and the bilge empty?
3. Fuel Level. Testing is best performed on 1/2 tank of fuel.
4. Boat Load. Have your average running load on the boat.
5. Condition of prop. Don't bother testing with a damaged prop.
6. Tachometer Accuracy. Use an accurate test tach. Dash tachs are often wrong.
7. Trim Level. Full speed is usually achieved with a slight trim angle.
8. Sea Condition. Choose a smooth or light chop day for testing.
9. Data. Know your engines rated WOT rating and be carefull not to over-rev.
Engines are rated at the factory for a safe RPM running range.
This rating is your "target" when selecting the correct prop.
If, for example, your engine decal says your RPM range is 4400 to 4600 RPM at WOT,
then 4600 RPM is your target.
The best prop for your boat will allow your engine (in this example) to reach 4600 RPM
when you have a slight trim angle and running at full throttle and full speed.
Always "prop" towards the high end of your RPM range.
Test run your boat at full speed and with a slight trim angle.
Try to get the boat to go as fast as possible.
Record your WOT RPM reading from your ACCURATE tachometer.
Now What?
Now you have some data to work with.
Props come in different sizes, designs and materials.
The data collected from your test runs and knowing how you plan
on using your boat will assist you in selecting the correct prop.
Prop sizes are measured in diameter and pitch.
If your old prop has a stamping 14-1/2 X 19 it means that you have
a 14-1/2" prop diameter and your pitch is 19".
The pitch is defined as the distance your prop would travel in one revolution
in a solid medium.
In general, a higher pitch prop will lower your WOT RPM and
a lower pitch prop will raise your WOT RPM.
One inch of pitch is about equal to 250 RPMs at WOT.
This is good to know!
Let's say, for example, that your WOT RPMs were 4850 but your max rating is 4600.
That means your WOT RPM's are 250 too high.
If you had a 19" pitch prop you would want to lower your WOT RPM by changing to a 20" pitch prop.
This extra inch of pitch would lower your WOT RPMs down to about 4600 which was your "target" RPM.
Don't concern yourself as much with the diameter.
Larger diameter props are better for slow speed maneuvering and larger loads.
Use the "250 RPM Per Inch of Pitch" rule to calculate your pitch.
It is important to note that pitch changes are to be done between props
with the same amount of blades and the same material.
So... if you had 3 blade aluminum prop (such as in the example above)
the pitch change would be to a similar prop design only in a 20" pitch size.
I Want a Faster Prop!
Yes, some props perform better than others.
A stainless prop will usually out perform an aluminum prop.
Stainless allows the prop design to have thinner blades and a more aggressive
blade design.
It is very common for the boat owner to change from an aluminum to a stainless prop.
Stainless props are less likely to be damaged from striking underwater objects.
If you fish the flats, stainless is the only way to go.
If you want top end performance, stainless is the only way to go.
When changing from an aluminum to a stainless prop,
you would usually drop down one size in pitch.
For example... if you get your exact rated WOT RPM with your 19" aluminum prop,
you would typically go with an 17" stainless prop of similar design.
Notice it's a 17" pitch and not an 18" pitch.
That is because props usually come in either odd or even sizes.
A "size" is what increments the prop comes in.
For example, a 3 blade Vengeance Stainless prop comes in 23", 21", 19" and 17" sizes.
A Laser II Stainless prop come in sizes of 25", 23", 21" and 19".
An exception to this rule is the Bravo One prop.
The Bravo One SS props come in even sizes of 36" down to 22".
Bravo One props have four blades.
If your boats RPM was perfect with a 19" aluminum prop,
you would not be able to buy a Bravo One prop to fit your need.
Which Stainless Prop is Best for Me?
Tough question!
Most boat manufactures have tested their boats with a variety of props.
Whenever possible, try contacting the boat Dealer or the boat manufacture
for prop recommendations.
Don't assume that the prop that you got on the boat from the Dealer is correct.
Sometimes the Dealer will just throw on a prop to get the boat "out the door".
Responsible Dealers take the time to test run and set up the boat with the correct prop.
This sometimes means numerous test runs with a large variety of props.
Different props have different characteristics.
Some stainless props, such as the Vengeance are good all-purpose props.
They fit a large range of applications with good performance.
Other props are made for higher horsepower boats. The Bravo One 4 blade prop is a good example
of a high performance prop for sterndrive boats.
Mercury Marine has a great webpage that has a Prop Selector Tool.
Go to the Prop Selector to get a good idea
of what prop would be best for your boat.
Would you like us to help you pick a prop?
No problem.
Just email us with answers to the following questions:
What is your boat manufacture and model?
What is your boat length?
What is your boats weight?
What style hull do you have?
How many engines do you have?
What type of engines are they?
Do you have your engine and drive serial numbers?
What type of drives do you have?
What are your drive ratios?
What props are you running now?
Do you have your prop part numbers?
What is your prop diameter, pitch and number of blades?
Are your props in good condition?
What WOT RPMs do you get with your old props?
Is your hull clean?
Are your engines running strong?
Did you use an accurate tachometer?
Did you trim the drive out for top speed and performance?
How does your boat plane?
How does your boat handle?
How do you usually use your boat?
Fresh water or salt water?
Notice that we didn't ask for the speed of your boat.
The speed is irrelevant.
When you have the correct prop that allows you to achieve your rated
WOT RPM the speed will fall into place.
Always "prop" for RPM..... not speed.
Try to be as complete and specific as possible.
Always include your engine and/or sterndrive serial number whenever possible.
We answer most requests withing an hour or less during normal business hours.
Otherwise, we will respond first thing the next morning.
Consider such items as:
Engine Year
Engine Serial number
Engine Size, model and number of cylinders
Drive model
Drive serial number
Quantity of parts
Parts Description
Parts Location
Size
Color
Material of part
Have you removed the part yet? It's best to disassemble what you need before ordering parts. Do you need any special tools? Do you have an adequate service manual? Do you have special shipping requests? What is your zip code and/or shipping location?Email us now.