Propeller Pitch ?

[bentpole]

Trashed my Prob,.Best I can tell my ol'prob- was a 10" dia X 15 degree pitch. (40 H.P. yamaha),Question is, if I went with a 10" x 13 would that give me less pulling power,But more top speed? Also have any of used the composite prob's? If so I'd like tyo hear the pro's & con's 0f it. Thanks.,,,,,

[CrappieHound]

No. I believe it is up gives you less pulling power but more speed. My boat has a 17degree pitch, if I go to 19 I get more speed but less pulling power.
I was told I can't go to 19 because I'm only running 5,500RPM's at full throttle. I'm not an expert on pitches and props, that's just what I was told by the service guy.

[roh1961]

If you change the pitch you will have the possibility of over-revving your motor if you change to a lower pitch. It's always best to have a tach to tweak for the best preforming prop. If you go to a higher pitch you might gain top speed but that's only if your outboard will turn it at a substantial rpm. You usually lose about 200 rpm going up one pitch and gain 200 rpm going down in pitch.

[Barnacle Bill]

You want a prop that will allow you to run the recommended WOT (wide open throttle) for your motor. Here is an excellent article on props: http://boatfix.com/how/props.html
Composite props are good for a spare only.

[crappietime]

My 90 came with a 19 pitch I bent it cause it was aluminum and on Old Hickory.I was turning almost 6000 rpms I went to a stainless 24 both was 3 blade.It is slow coming out of the hole but it still turns in at 5500 but only speed of 43mph.

[bobberwatcher]

The way it was explained to me is if it is a 17" prop, it turns 17 times per foot WOT, 19" - 19 times per foot, etc. The higher pitch prop, the more power, but less speed. Don't take that to the bank, but just what I have heard.

[Barnacle Bill]

The way it was explained to me is if it is a 17" prop, it turns 17 times per foot WOT, 19" - 19 times per foot, etc. The higher pitch prop, the more power, but less speed. Don't take that to the bank, but just what I have heard.

This may be true only if both props keep you within the recommended WOT range. Go here and page down to operating range. http://boatfix.com/how/props.html It explains it a lot better than I can.

[Slipcork]

Trashed my Prob,.Best I can tell my ol'prob- was a 10" dia X 15 degree pitch. (40 H.P. yamaha),Question is, if I went with a 10" x 13 would that give me less pulling power,But more top speed? Also have any of used the composite prob's? If so I'd like tyo hear the pro's & con's 0f it. Thanks.,,,,,

How many rpm's are you turn with the 15? If you go to the 13 you will have more power and (maybe) less speed. The pitch means (without slipping) the prop moves forward 13 or 15 inch per one full turn of the prop. If you go to big the motor will not be able to turn the prop. If you go smallier, the motor is able to turn it more and you get the best of both worlds. I run a 1984 40hp Yamaha with a SS 15". Pull kids on knee board and will run 46 mph with just me in it.

[ShortStorie]

Ya got it backwards, Bobber... A 15" prop will (in theory only) move the boat forward 15" per revolution of the prop. A 17" will (in theory again) move the boat 17" per revolution... ("higher" pitch). I wouldn't stray more than 2" either way from the mfg recommendation on a small engine. Too much prop and you'll bog the engine and go slower... IBNFISHN was right about prop turning max recommended rpm at sustained WOT. A heavy boat will require a smaller pitch prop than a light boat. Many of the Go Fast guys run a higher pitch prop in the cold months because the engine produces more power then.
2 stroke performance drops dramatically in hot weather. My Merc 90 will turn 6000rpm when I'm shivering but tops out at 5500 in T-shirt weather (20" Lazer II).
Going from aluminum to stainless effectively increases pitch because aluminum flexes way more under load. For that reason, the composite props are strictly an emergency "get home" prob.

[Gadget Man]

I think the theory of pitch is "the number of inches the prop would advance per revolution with no consideration for slippage." Per ShortStorie and Slipcork above.

The lower number will give a better "hole shot" and the bigger number will give less of a "whole shot," but a better top end speed.

I would defer to a professional for guidance regarding your specific boat and motor set-up.

ShortStorie talks about aluminum, composite, and stainless props above. He is right on the flexibility of aluminum/composite versus stainless. However, my mechanic always points out that aluminum/composites have more give than stainless when you hit something solid. The stainless prop doesn't give, but sometimes the mechanicals inside the motor do! Give consideration to where you run before making the prop type decision.

I do prefer stainless, but I know the waters very well where I rboat. There isn't much in the way of underground stumps and changing bottom conditions.

Good luck in finding the prop that is right for your needs...