Prop question

[Douglasdzaster]

Hello my tin boat family.
It’s been a year since I’ve been on the water or even touched my boat.
I’m back with an almost clean bill of health. Close enough anyway.
Thanks to all the preventative maintenance I uncovered the old Catfish hunter and all is well so back to where I left off. It’s a prop question so I hope I’m in the right category.
Yamaha 1992 40 hp 3 cylinder 2 stroke. Current prop 10 1/8 X 15. WOT 6500 rpms.
I was going to simply get a 10 1/8 X 17. But I can’t find such an animal.
I’m trying not to go up in diameter and lose speed so I thought I’d ask for some opinions on a couple of options I found.
I found a 10 X 17 and 10 1/4 X 14 or 10 3/8 X 14. There’s a 10 1/2 X 13 but I’m afraid of that much increase in diameter.
I don’t have a place near me that I could go try different props. The closest place to even get an outboard worked on is over an hour away. I have done all the work myself and ordered everything online to bring it back to life. I removed a lot of weight replacing the floor and using all lithium batteries.
I’d appreciate any wisdom or ideas.
Thanks: DDZ

 

[KMixson]

Just my opinion. If you are wanting to go faster, the 10 X17 sounds to be the best choice. That pitch is 2" further than your current prop but at a 1/8" decrease in diameter. I do not know if the decrease in diameter will matter that much. 6500 RPM sounds like it could use more pitch to me or a larger prop if you wanted to go that route.

 

[Stand Up]

Hello my tin boat family.
It’s been a year since I’ve been on the water or even touched my boat.
I’m back with an almost clean bill of health. Close enough anyway.
Thanks to all the preventative maintenance I uncovered the old Catfish hunter and all is well so back to where I left off. It’s a prop question so I hope I’m in the right category.
Yamaha 1992 40 hp 3 cylinder 2 stroke. Current prop 10 1/8 X 15. WOT 6500 rpms.
I was going to simply get a 10 1/8 X 17. But I can’t find such an animal.
I’m trying not to go up in diameter and lose speed so I thought I’d ask for some opinions on a couple of options I found.
I found a 10 X 17 and 10 1/4 X 14 or 10 3/8 X 14. There’s a 10 1/2 X 13 but I’m afraid of that much increase in diameter.
I don’t have a place near me that I could go try different props. The closest place to even get an outboard worked on is over an hour away. I have done all the work myself and ordered everything online to bring it back to life. I removed a lot of weight replacing the floor and using all lithium batteries.
I’d appreciate any wisdom or ideas.
Thanks: DDZ

Welcome back @Douglasdzaster .
I hope you're feeling better into the future. The fish miss you!

 

[FuzzyGrub]

Welcome Back, glad you are feeling much better and ready to work on our boat!

What is your WOT speed, and what issues are you having with the current prop? For example, if it is too high of rpms for the motor, and want more speed at the sacrafice of some hole shot, more pitch is generally the answer. More cup added to your current prop can work as well. Or just let off a little throttle and save it for when you have a heavier than normal load in the boat.

My recommendation is to wait on the prop, until the boat is finished and you can retest.

If you are comparing pitch/diameter between different brands/models, the results will vary, due to the other aspects of a prop, including rake, cupping, #blades, etc.

With the same brand/model, going up in pitch usually means a slight decrease in diameter. No problem there.