Prop pitch vs weight

[redfishlost]

Is there anyone out there with a similar boat with this engine.....I dont have a tach or dealer to advise me.
Please reply to post if you have the same or similar combination!



I currently own and enjoy a 2005 K14 Sundance skiff,powered by a 2005 25 hp F25 Yamaha four stroke engine.
The stock prop is 9 7/8" diameter x 9 pitch,and is aluminum.
The boat planes easily but doesn't seem to have very much speed.
It seem as though there is more power but much like a race car which has too low a gearing for the distance.
What would be a good selection of prop size and pitch for this combination of boat & engine?
Also,would a stainless steel prop provide any significant benefit?
Thanks!
Redfishlost

[Reel Insane]

First off, I would find out what the maximum RPM's your engine is designed for. Second, I would install a tach to find out how many RPM's you are currently turning. From there you can determine what pitch prop would produce the best performance. I would prop to the high side as this will give you better fuel economy. I try to keep my max RPM's about 200 below max spec.

[Oz Rosco]

Hey Redfish,
What Reel Insane said is correct.
And from the practical experience I have had with props . . . a 9 pitch will get you out of the hole faster, but will have a limited top speed.
If you were to try a 12 pitch, your hole shot would be weaker, but it will have a better chance of running out to it's speed potential without experiencing the race-car scenario you described.
I had a 9 on an old motor, and swapped it for a 12. The hole shot was weaker, but the boat was able to " stretch out " with a lot less effort.

[redfishlost]

prop pitch vs weight

Thanks for the input guys. Please view the attached link for my reference to a prop of 9" x 11 1/4".
Slightly larger boat with greater speed than what I am experiencing currently.
I am trying to stay within a tight budget as we are all doing during these hard times.
But I have a tach from a racing kart which may work.
Max rpm rating for the F 25 is 6,000 It is a wild cat out of the hole but I would much rather have top end over the hole shot
Redfishlost


http://www.yamaha-motor.com/assets/p...sa8e76.tmp.pdf

[99yam40]

Performance Bulletin Home

see if this will give you any info

[redfishlost]

pitch vs weight

Yes, this is the same bulliten I have attached to this thread.
Was somewhat similar.....only my payload is less and they are using a pitch of 11 1/4" which is where my suspect target pitch may well be close.
Redfishlost

[mouse action]

how does one go about finding out the pitch of the prop I have ?

[redfishlost]

I have found on both my Johnson & Yamaha engines that the pitch & diameter is molded into the prop,either @ the hub or on backside of propeller blade.
This may not be true of all props,but this is location on my (2) engines.
The first # is the diameter and the second # is the pitch.
I hope this helps you!
Redfishlost

[mouse action]

big help.thanks

[bigem1]

First off, I would find out what the maximum RPM's your engine is designed for. Second, I would install a tach to find out how many RPM's you are currently turning. From there you can determine what pitch prop would produce the best performance. I would prop to the high side as this will give you better fuel economy. I try to keep my max RPM's about 200 below max spec.

You really need a tach to do anything, but; guesswork with a prop. Multi adjustable pitch blades are around,but; I've always gotten help from my servicing dealer...

Have A Great Day!!