[bobsled]

Before we begin to list the actual steps that one must take to determine the size of boat props, let us discuss the 2 primary players in the boat prop measuring world. They go by the name of diameter and pitch. These numbers go together like water and boats, marinas and money, and fish and water. The two elements that you always want to be aware of are the diameter of the prop, as well as the pitch of the boat prop. For example, if a boat propeller has a pitch of 24" and a diameter of 10, is would be known as a "10/24" propeller. The best place to find out what kind of boat propeller that you have is to look at the hub of the boat prop. This information is usually written conveniently on the hub of the boat propeller. Unluckily, because of the erosion that has taken place because of water, constant use, and other mitigating circumstances this number may no longer be visible. Also, if the person who owned the boat before you did had a propeller that was unique, this information can be next to impossible to find.

[fkuro27]

Determining boat prop size is not as hard as it may seem. If you have always wondered how big your boat propellers were, you no longer have to wonder. You have the ability to measure the exact size of your boat props, if you just have a few simple tools at your disposal. In this article, we will discuss how everyday boaters can determine the size of their boat propellers very easily.

[MrFlibble]

1. The first thing that you need to do is to measure the distance from the center of the hub to the farthest point that can be found on a specific boat prop blade. This is also called the boat prop radius. Remember that the diameter of the boat prop is double the radius. In other words, if you have a boat prop that is located 8 " from the hub's center to the outermost point from a single propeller blade, you know the diameter must be 16".
2. 2. Assess the prop pitch by seeing how the boat operates at 50 percent of its speed level. It is a good practice to write down the actual speed and precise number of RPMs which can be determined by looking at the boat's tachometer.
3. The next factor that we will look at is the prop pitch. The pitch of a boat propeller is calculated using inches. You can figure this number out by determining the distance in inches that one revolution of the boat propeller will cause your boating vehicle to move in the forward direction. These numbers must be rough calculations because of various factors such as, the shape of the hull, the amount of salt in the water, the temperature level of the body of water, and other circumstances that are beyond a boater's control.
4. Next, a boater must find out what the gear ratio of the boat's power train is by consulting their owner's manual online or in paper format. When figuring out this information you just need to go with the first number of the ratio that is expressed in order to figure out the pitch of the boat propeller.
5. Finally, you can figure out the pitch of your boat prop by simply dividing the amount of RPMs by the information that was derived from the boat's gear box. Do not forget to use the tachometer to assist you in determining the gear ratio. Once you have the numbers you need, you simply multiply the numbers you have obtained by 1.2 and then divide that figure by the speed of your boat.

here

[curmudgeon]

more

[costner1367]

here

[inertia]

[links]

[Yort]

on all the props i have installed or replaced the size and pitch was inscribed on the inside of the prop , so you have to remove it.
:redface: here

[Wayne33botha]

Re: How do I determine my current propeller's pitch? [links]

[alexaverbuch]

Re: How do I determine my current propeller's pitch? more

[TORNS]

Re: How do I determine my current propeller's pitch? more

[bitanarchy]

Did you try trimming your motor out a bit? Porpoising is normally from a bow down attitude. That would also slow the hole shot. [links]

[ElidiaI39]

The hub is the center of the boat propeller where the blades attach. The center of the hub will slide over the propeller shaft. In many cases this is the point where exhaust exits the engine. [links]

[brightside]

Cavitation is any erosion, pock marks, or irregular edges on the surface of the propeller. When a pocket of air forms on the backside of a propeller blade, the impact of air bubbles on the actual blade causes cavitation. This usually happens when a propeller’s RPMs are too high for its design.

[bradford1Merrill]

The kind of prop your engine needs depends largely on how you’re using your boat. Whether fishing, cruising, or water skiing, different applications place different loads on your engine. Regardless of application, the key is to keep your engine within its factory-recommended wide-open throttle (WOT) RPM ratings, which are easily found in your owner’s manual. Selecting a prop with the right pitch, diameter, rake, surface area, and contour for your engine will keep you within your RPM range.

[ggs]

• Wide range of performance options
• Our premium stainless steel line
• Large selection across most motors with PowerTech

[BitcoinFX]

Regardless of the reasons to opt for a three or four-blade prop, doing on-water testing in repeatable conditions is the way to go. On-water testing is the best way to achieve the most accurate blade selection for your boat and its particular application. Plus, it’s another excuse to get out on the water! [links]

[donpdonp]

Re: How to tell what pitch Prop I have [links]

[rickiehenry1]

Some of the (I called them L-Cheapo) props need a hub kit with them. I have never used one.
The pitch should be stamped in the face of the hub.
Or you can take it to a prop shop and they can clean it up and also gauge it and tell you the exact pitch.

[fabianhjr]

How can I tell what prop I have on my 2006 Merc 115 ELPT 4S motor? I am the second owner. This motor came from dealer installed on a Premier 23' 225 Pontoon Boat (I bought this setup from original owner). It pushes this pontoon boat fairly well but I notice other pontoon boats of same length with similar or smaller motors seem to run a bit stronger/faster.

[Mark Petrov]

I ran a prop wizard and it said a 14 X 13 for water sports or 13 3/4 X 15 for speed. I'm just trying to figure out what the factory prop is. Would it be setup with a particular prop for a Pontoon? The existing alum. prop also has some heavy nicks and gouges from all of the stick etc. in the lake. I also notice that a discount prop retailer stated I must buy a "hub". Is that a common set up to have to use this hub (I'm guessing it is and some kind of a splined adapter?)

[qaz22]

Anyway. just looking for some insight and i a new prop might help the boat run better. [links]