Non-thru hub prop

[CajunBubba]

I need to find a non thru hub prop with a 13 tooth spline. I have a 1982 25 hp Evinrude, on which I have installed a 35 carb. Currently, I have a 12" pitch prop on it. I want to increase the pitch of my prop. I have plenty of torque, but the boat is slow. Does anyone know where I can find this style prop in a 14" pitch?

Thanks

 

[steelespike]

Re: Non-thru hub prop

A 14 will be difficult to find.Does it appear to over rev?What is the present speed?
Do you have the present wot rpm and speed? Its difficult to tell what you need
without performance specs. A tinytach and a gps can get you the info.
If you get it to us we can tell better what you need.
Depending on the year of the 35 and 25 I think the gear ratios may be close.
The 35 uses a larger diameter and I think different hub. If the 35 prop will clear the lower unit you may be able to have a 25 hub pressed into it.

 

[CajunBubba]

Re: Non-thru hub prop

A 14 will be difficult to find.Does it appear to over rev?What is the present speed?
Do you have the present wot rpm and speed? Its difficult to tell what you need
without performance specs. A tinytach and a gps can get you the info.
If you get it to us we can tell better what you need.
Depending on the year of the 35 and 25 I think the gear ratios may be close.
The 35 uses a larger diameter and I think different hub. If the 35 prop will clear the lower unit you may be able to have a 25 hub pressed into it.

[ The boat is a 16' aluminum jon boat. According to the GPS, it runs 21 mph. However, it runs 20 mph with three grown men in it, with an ice chest and fishing tackle, so it seems to have plenty of torque. It doensn't seem plane well, though. A friend of mine with the same boat has a newer 25 evinrude, and his boat planes well, and gets up to 30 mph. I feel that when I installed the 35 hp carb on my powerhead that I gained torque. I did check the gear ratio on the 35 hp that I salvaged the carb from, and you're right, they are almost the same. The 35 hp, however, had a larger diameter prop, and was a higher pitch. It actually had a 15" pitch prop, but it was a thru hub exhaust. Thanks for the advice, and I'll see about getting a tachometer.]

 

[smokeonthewater]

Re: Non-thru hub prop

Yep, you definitely need rpm before making any changes and you can pick up a tinytach on ebay for $15

You may be able to get your current prop reworked for a little more pitch and cup but get rpm's first.

FWIW torque is not really the right term... it's hp that will get you going.... more torque will swing a larger diameter prop and drag more weight at the same speed but hp turns a higher pitch for more speed.... not very scientific but you get the idea

 

[steelespike]

Re: Non-thru hub prop

What year is the newer 25. If its an Evinrude in the same decade as yours it is esentually the same motor.
If its a 4 stroke or much newer we're talking apples and oranges.Your 25 is capable of 30 without a 35 carb and I'm almost positive that a simple carb change will not make much difference and may just create trouble.While some motors do have restricters I don't think your 25 is one. I hope you don't figure a carb change will increase hp by 40%.to 35.
We need to know the year and make of your friends motor,size of the prop,rpm and is the boat a bare bones jon.
If his motor is a 25 Evinrude it would have to spin over 6000 rpm to do 30.possible but I don't think on a 16ft Jon.
If your motor isn't making enough rpm it's a motor issue not a prop issue.Hopefully you can get a tach and we'll figure it out.