Some Prop Advise Needed..

[sammy29926]

Hi Everybody,
I ahve a2001 johnson 150 on a 2001 Larson Boat. Prop on it is a Aluminum 15 1/2 and 15 pitch. I need a new prob since th eone on the motor has bunch of nicks and not straight. I would like to get a used one but on ebay all i can find is 15 dia 17pitch. or 14 1/2 and 17 pitch.. My question is what is the diameter of a prop and pitch of a prop effects eachother.. Can i intall asmaller diameter prop with higher pitch?
Thanky ou
Sammy

 

[Silvertip]

Re: Some Prop Advise Needed..

If diameter and pitch didn't affect the performance of a motor then there would be no need to have all the various combinations. Buy the prop specified for your motor. Diameter is a function of prop design. Props are also designed in various diameter "ranges" since a small motor will require a much smaller diameter prop than a mid size or large outboard. If you look at various pitches within a range of props for your motor you will see that diameter decreases very slightly as pitch increases. The long and short of this is that you first select a prop "range" that is specified for your engine. YOu then select the pitch you need. Diameter will take care of itself. Now if you have a 50 HP Evinrude or Johnson for example and you attempt to install a 15 inch diameter prop on it, you will quickly find out that it hits things. Prop diameter will only change about an inch within the range of pitches for your engine. The biggest mistake people make when buying a prop is not knowing what the wide open throttle rpm is with the current prop. Without that knowledge you cannot deterime whether you should have the same prop, or one with more or less pitch. The prop is the transmission for your boat and it has only one gear so it must get you out of the hole, cruise comfortably, and allow the engine to operate at or near the upper end of the manufacturers recommended rpm band.

 

[Dhadley]

Re: Some Prop Advise Needed..

You'll be fine with any of the above props. Depending on what brand and style your prop is it may have been a prop built for a specific purpose and I doubt it was specifically for a Larson.

Diameter can have a big effect on how the prop performs, just depends on what the prop was intended for. If you go with ss you'll probably end up with a 3 blade 14 1/4 x 17 and will be able to raise the motor some. Assuming the rpm is right with the prop you have.