prop size help please

[zetecor]

Hi I have a 13ft dell quay dory with a 1989 40 hp 2stroke mariner.
The prop i was using was a bit dammaged so i took it to be repaired, the guy said it may be the wrong pitch for the boat, ie the engine may be over-reving, I have no rev counter. the boat picks up very quickly on this prop.
The number on the prop is: 10-3/4 x 12
I have another prop which I have not tried it looks a little smaller with the following number:
48 73136 a40l 13p as the two numbers are so different I am struggling to make a comparison.
Can anyone help me with a comparison between the two props.

thankyou very much

 

[180shabah]

Re: prop size help please

all I can tell you is that one is a 12" pitch and the other is 13" pitch. Without a tach nobody can tell you if a prop is correct or not. maybe a guess, or I usually see.... but it is just a guess with out WOT data.

 

[zetecor]

Re: prop size help please

I figure that the untried 48 73136 a40l 13p is a 10" 13pitch.
will this give more acceleration or more top end than the 10 3/4 12 pitch?
if its suitable.

 

[180shabah]

Re: prop size help please

will this give more acceleration or more top end than the 10 3/4 12 pitch

Probably neither.

 

[zetecor]

Re: prop size help please

hi, do you mean it will be about the same? or poorer in both respects?

thanks

 

[steelespike]

Re: prop size help please

A Tinytach is about $40 and easy to install. That and a gps you could really hit the prop on the nose. rpm without speed only tells if it is lugging, right on, or over reving.add in the speed and you can tell if the whole setup is working at its best.
The 13 will lower your rpm a little Without rpm figures no way to know if your rpms are right.

 

[zetecor]

Re: prop size help please

I guess its suck and see then.

thanks