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.

 

[Douglasdzaster]

Thanks guys I appreciate everyone of you.
Fuzzy Grub I may be jumping ahead. What I have now is actually a prop I ordered by taking a guess. The prop that came with the boat will top out at 5500 rpms and 33-35mph. But it’s in sad shape. The blades have cracks etc. The numbers look like someone tried scratching them off. All that’s left of the diameter is 1/8 and the pitch is 16.
The 10 1/8 X 15 I bought fully loaded comes out of the hole great and at 5500rpms I’m going 26-28mph.
After reading y’all’s comments I’m going to to hold off. I still need to replace the casting deck on the bow and if there’s room I may add a little storage when I do.
Also I’m going by a little tachometer that wraps around the spark plug wire so there’s more guessing happening with that as well.

As always I get excited when doing something to the boat and need to slow my thinking process. It’s great to be back here.

I really just need to check the whole rig out and get back on the water right now. Then the rest will come.

I’m on a new mission. I’m now one of the leaders for the local Kids outdoor zone (KOZ) chapter. We’re based out of the church I go to. We take young men ages 8-18 most of which don’t have a father figure in their lives. We teach them how to hunt and fish as well as other skills along with some life lessons so they can be good husbands and fathers (leaders).
I just booked a lodge for April in Matagorda for some saltwater action.
It’s going to be a nice break for us men and the boys.
They’ve been working hard the last few months learning survival and how to build shelters. Before that we spent time helping out with clean up and repairing a house for a lady that lost her husband.

 

[FuzzyGrub]

I’m on a new mission. I’m now one of the leaders for the local Kids outdoor zone (KOZ) chapter. We’re based out of the church I go to. We take young men ages 8-18 most of which don’t have a father figure in their lives. We teach them how to hunt and fish as well as other skills along with some life lessons so they can be good husbands and fathers (leaders).
I just booked a lodge for April in Matagorda for some saltwater action.
It’s going to be a nice break for us men and the boys.
They’ve been working hard the last few months learning survival and how to build shelters. Before that we spent time helping out with clean up and repairing a house for a lady that lost her husband.

I commend you, sir! That is a great public service you are doing.