# One last prop for the Plytanic



## firecat1981 (Nov 27, 2007)

So for a while I have been using the stock yamaha prop on my F20 (4-stroke 20hp). It's been ok, and the best of the three props I have from the last skiff. Well after years of sand bars, oysters, and submerged logs, I think she is finally done. I'm not going b to have the skiff to much longer, but I need her to work hard until the end.

The stock prop, 10" pitch, got me about 26mph at around 5600rpm if memory serves fishing solo. Add in a load plus a buddy and I was still getting 22mph at around 5100rpm. Acceleration was decent, holes hot was ok. I thought about another stock prop with 9" pitch, but they don't make many and yamaha wants a premium for them.

So I have 2 other props I retested, both are Solas Amitas. One is a 9" 3 blade, the other is 11" 4 blade.

The 3 blade 9" pitch is over reving so far it hits the limiter! If I back off a bit at 6-6100rpms I'm only getting 22mph. Hole shot is ok as is acceleration, but not as good as the yamaha. I'm guessing massive slip.

The 4 blade 11" pitch is lugging a bit. Unloaded flying solo she will run 25mph at 5200rpms. Hole shot is slow as is acceleration. I loaded the skiff with what I could (cooler full of water, 2 5 gal buckets full of water, livewell filled up....) and she slowed down to 20mph at 4850rpm. Obviously performance suffered.

So now I have to make a choice pretty quickly. Do I stick with the 4 blade and drop a few inches in pitch to 9"? Do I go up to 10 or 11" on the 3 blade? Do I try another prop like a turning point in 9"? Obviously I don't want to dump much money into a prop I'll only use for a few more months, and selection is limited. Thoughts?


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## yobata (Jul 14, 2015)

https://dansdiscountprops.com/BuyNow/Solas-Prop-Yamaha.cfm#Yamaha-Prop
$58 plus shipping ($8-17)

9.9 11" amita3 (aluminum) B series


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## firecat1981 (Nov 27, 2007)

It's gotta be an A series, the F20 uses a 8 tooth spline.

So you think the 3 blade is better then the 4? I'm pushing a pretty heavy load at times, another 2 guys plus gear.


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## damthemainstream (Apr 11, 2017)

I think you went the opposite direction with blades and pitch. I think a 9" 4 blade or either 10 or 11 in the three blade would be good. The stock Yamaha prop is cupped, so the 10" pitch on there might be a little more than the 10" on the Solas.


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## firecat1981 (Nov 27, 2007)

Those were left over from my old boat when I was trying to figure it out. I was just using them to get a baseline to help me decide the direction I need to go. 

I agree either a 9" 4 blade, or 10" 3 blade is what I'm thinking. The 4 blade even with it lugging still managed a better top end, so I'm leaning that way.


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## DuckNut (Apr 3, 2009)

Why would you buy a new prop when you have 2 already and the end is near. Neither of these are ideal per your description but the 10" is. You have a baseline with the 3 props and the 10" seems to perform best for the Plytanic.

Buy a new one and not have it work for your new build and you just have a useless prop sitting on your shelf. Use what you got and deal with it until the new ride is done. Then using the baseline test with the 2 existing props and if similar results, get one in the middle.


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## firecat1981 (Nov 27, 2007)

The 10" is shot, it's now got a large chunk missing from a blade, and is ground so far down it's probably lost 1/4" off the blades.
This motor will not be going on the new skiff, she is getting a new 60hp. The current performance is so bad with the 3 available props now I feel I have to make a change or risk damage to the motor. Really we are only talking about $65 with shipping.


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## DuckNut (Apr 3, 2009)

FC - how many spline is your prop? I may have one lying around here. Not new but unbeaten.

Edit: 3 blade stainless


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## DuckNut (Apr 3, 2009)

I was just thinking. Can you have your stock one rebuilt and have them add some cupping? That would give you the hole shot and slow the rpm's a tad bit.


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## firecat1981 (Nov 27, 2007)

Thanks DN, I already got a new prop and tested it. Mine uses the 8-spline shaft. I contacted a few prop shops a while back and they said they can add cupping to the aluminum props, but they don't recommend it. Metal fatigue builds faster in aluminum I guess, and it would cost more then the prop is worth to rework it.
This will be my last foray into aluminum. I'll budget $3-400 for a nice ss prop on the next skiff. 

Here's how the new prop is going to work out. It's not perfect, but I'm fairly happy. The 4-blade 9" is still hitting the Rev limiter with the boat unloaded, but not as easily. So going down 2" in pitch gained me over 1000rpm. 
So I was getting 23.3mph @ 6000rpms. I lost a few mph on the top, but holeshot was pretty good as was acceleration. 
I tried loading my normal solo load, livewell and cooler full, and was around 22.4mph @ 6000rpms
I loaded down the boat with an additional 150lbs and was now getting 20.3mph @ just under 6000rpms. Holeshot and acceleration remained the same throughout.
While not perfect this prop seems to take additional weight much better, which is good cause the majority of my trips left this year are camping and scalloping, which gear and crew.

I think this will take me to the end of the plytanic saga. I hope nothing stops me from the new build this year.


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## yobata (Jul 14, 2015)

firecat1981 said:


> Thanks DN, I already got a new prop and tested it. Mine uses the 8-spline shaft. I contacted a few prop shops a while back and they said they can add cupping to the aluminum props, but they don't recommend it. Metal fatigue builds faster in aluminum I guess, and it would cost more then the prop is worth to rework it.
> This will be my last foray into aluminum. I'll budget $3-400 for a nice ss prop on the next skiff.
> 
> Here's how the new prop is going to work out. It's not perfect, but I'm fairly happy. The 4-blade 9" is still hitting the Rev limiter with the boat unloaded, but not as easily. So going down 2" in pitch gained me over 1000rpm.
> ...


what are you planning on building? wood and epoxy or trying something different this time?


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## firecat1981 (Nov 27, 2007)

Sticking too epoxy/ply composites. I have literally beat the hell out of this boat over the last 7 years and she has held up great even though she was built light. Why mess with a winning formula.
I've got plans for a bateau.com FS17, center console, slightly over powered with a 60hp zuke. 
This boat will have a totally different program, think mini bay boat rather then super skinny terror.


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## yobata (Jul 14, 2015)

firecat1981 said:


> Sticking too epoxy/ply composites. I have literally beat the hell out of this boat over the last 7 years and she has held up great even though she was built light. Why mess with a winning formula.
> I've got plans for a bateau.com FS17, center console, slightly over powered with a 60hp zuke.
> This boat will have a totally different program, think mini bay boat rather then super skinny terror.


I was just checking out the Study Plans for it, looks good! The recommended power is 25-50hp (although the pics in the Study Plans show it with an F60 lol). Have you thought about which motor you will use?


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## firecat1981 (Nov 27, 2007)

I want a white suzuki 60. I'm going brand new. It's the same weight as the 50hp, so why not get the 60hp for a few hundred more. I'd rather have it and not need it... package is right around 6k, with the prop, controls, digital color guage, rigging, and sea trial.


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