Prop Help, 73 40hp Evinrude

1506cmo18

Petty Officer 2nd Class
Joined
Oct 6, 2009
Messages
114
Looking for a new prop and am wondering if a different pitch or size would help my take off? In my Evinrude service manual it list about 5 different props I can use but dont know if a smaller pitch is better or worse?? Or if a smaller size is better or worse?? Any help would be greatly appreciated!
CMO

6 questions to answering your prop question
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless and as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight

1) Current prop is bent, chipped and has slow take off
2)Aluminum, stock evinrude??
3)10 1/2 x 13, 3 blade
4)Book says WOT @ 5000rpms (no tack or speedo)
5) 1974 Head, 1973 lower end, 40 hp Evinrude Short shaft
6)14ft fiberglass, 4 passenger speed boat, 500lbs?
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Prop Help, 73 40hp Evinrude

Without your max rpm and speed its very difficult to make a prop selection.
A tinytach,about $40, is easy to install a gps or a friends boat can check your speed.
You could get your prop repaired and run a couple of tests.get max rpm and speed one aboard.
If it struggles to plane with one aboard and a 13" pitch I would suspect issues other than prop selection.
 

1506cmo18

Petty Officer 2nd Class
Joined
Oct 6, 2009
Messages
114
Re: Prop Help, 73 40hp Evinrude

It does not struggle to plane, I would just like a little more take off out of the hole.

My propeller shaft has no splines on it and all the new propeller need splines. Does anyone know where I can get the old style propellers? Mine is just a plane shaft that the propeller slips over and is pinned on. Ill keep the same pitch and size just need a new one.
 

1506cmo18

Petty Officer 2nd Class
Joined
Oct 6, 2009
Messages
114
Re: Prop Help, 73 40hp Evinrude

Turns out Iboats discontinued props for my motor.
 
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