Prop language

[Stotch]

Have read the various posts about prop selection, different blades and pitches. But am confused as to what the numbers stand for. Eg. a 13-1/2 x 17 what does this mean. And what should I consider ( alum. or SS ) for a 100hp Mariner 2 stroke.

[Kaz]

The first number is the diameter and the second is the pitch or the distance one turn will propell the boat. 13 1/2 = diameter 17" travel per rotation. Kaz

[Kaz]

PS Stainless is very expensive... Alum can be repaired for about sixty bucks. Kaz

[Scott D]

There are a lot of people out there that know a lot more than me about props, but I thought I would state what I think the answer to your question is:

The first number would be the diameter of the prop from the outside tip of the blades. The second number is usally the more important number. It is the pitch. A 17" pitch prop will spin faster (higher RPM's) than a 21". I believe that the pitch is the distance traveled (theoretical) in inches for each revolution of the propeller. You can calculate how fast your boat can go with a given pitch prop with a formula that takes into account the lower unit gear ratio, the pitch, and the RPM's; then you can factor in prop slip (usually around 10%) to estimate your speed.

As far as aluminum vs. stainless - Stainless props will give better performance and resist nicks if you hit something real lightly. The drawback is that since the stainless props don't bend if you hit something, then you could suffer lower unit damage more easily if you strike an underwater object than if you use an aluminum prop.

I would say that if you want better speed and you are careful when you run your boat, than the stainless props are the way to go. If you run your boat in water that you will likely strike underwater objects you may want to consider the aluminum props.

[Scott D]

Looks like KAZ beat me to a response. I guess I have to learn to type faster or say less. He posted while I was typing my response. Looks like we agree on the pitch and diameter though.

[Walleye2k]

Don't know if you guys have tried one, but I just found and Ordered a "PERFORMANCE ALUMINUM PROP" The Company that makes them is solas... www.solas.com In the approximate size as mentioned in the first post, 13 X 17 a Typical ALuminum Replacement is $100, a Stainless is $300 The solas Prop I paid $130 for. I will be trying out the prop this weekend and post results compared to the current Prop. The Bass Boat Boards have a lot of info on Props, Bass Guys are more speed freaks.