Help find me a new prop

Toddk9

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Ok guys this is what i have:
2017 Bennigton 21 SLX w/ Yamaha 115 SHO motor
The express toon package
Motor mounted to very bottom hole
Currently running the Yamaha 14x13 SS prop

With the GF and I (most common for weight when we go out) the motor runs 6200 RPMS (redline?) and about 32 MPH

I was thinking of going to the Mercury Spitfire 4-Blade aluminum Prop 13.4x15 to lower my RPM's and maybe give me more on the top end. My pitch gets bigger but I lowered my diameter. Does somebody else have another recommendation for the prop?

Should I also raise my motor 1 or 2 holes since it is a express package and they tend to sit lower in the back compared to the SPS package?

Any other thoughts?

Todd
 
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Michiman

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Or you can contact Ken @ propgods.com and see what he recommends.
 

Remediation

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I recommend calling Ken also. i used him and am pleased with the prop.
 

PartyBarge

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From your data, you have a very good combination now. What are you wanting to do/change? Here's what I found:
2017 Yamaha VF115 VMAX SHO Outboard Motor

Year 2017

Manufacturer Yamaha Marine

Model Name VF115

Trim Name LA

Generic Type (Primary) Four Stroke

Engine

Engine Type In-Line Four Cylinder

Engine Power 115 HP @ 5500 RPM

Alternator (Output): 35 Amp

Displacement 1832cc (111.8 ci)

Gear Ratio (Primary) 2.15:1

Lubrication Wet sump

Fuel Type Induction: EFI (DOHC)

Ignition System: TCI Micro Computer

Oil Type (Recommended): Yamalube® 4-M (See Owner's Manual)

Fuel Type (Recommended): Regular Unleaded (Minimum Pump Octane 87)

Capacities

Oil capacity 3.2 liters / 3.0 liters w/without filter

Range

Note Full Throttle RPM Range: 5300-6300 rpm

Dimensions

Length Shaft: 20"

Bore 3.19 in. (81 mm)

Stroke 3.5 in. (88.9 mm)

Weights

Dry Weight 377 lbs


Your WOT calculated slip is ~11%. That is pretty good for a pontoon and is great if you have a standard 3-blade ss prop...it's about as expected if you have a prop designed for pontoons (yes, Yamaha has those). Also your WOT RPM is in the desired range. Your current setup is good for a good top end and should accelerate well too.

Lifting the motor a notch or two "might" bump the top end (can't say for sure for your boat), but at some point that increases slippage too (maybe with even one notch). That would likely move WOT out of the desired range pushing you toward a 4-blade prop (if you don't already have a pontoon prop). Consider that you might be better served to buy motor wedges to get the bow down, particularly at less than WOT. Just 2 degrees of additional "tuck under" can make a big difference.

OK, all that said, here's what I learned with our combination: Tried all motor heights from full down to full up (drilled a couple more holes for that). Current setting is two holes up from motor sitting on the transom. All standard Yamaha 3-blade AL props except one (13 to 15 pitch) have 30+% slippage @ WOT at any motor height. However the good news is a switch to a Quicksilver Nemesis pontoon prop (4-blade AL twin of the Merc Spitfire). A 13p Yamaha 3-blade ran ~6300+ RPM. A 13P Nemesis runs a nominal 5500 RPM with better speed and, roughly, half as much calculated slip (yes, that's a drop of 7-800 RPM with the same pitch prop). BTW: I also now have about 2 degrees of additional down trim using a clearly red-neck solution to bow high low speed deck angle. For our pontoon, better deck angle reduces drag and gives just a little more speed at anything below ~4000 RPM.

If you still feel the need to tinker (you might surmise I would completely understand that), get some motor wedges to put in as you lift the motor a hole or two. Next, if you don't already have a pontoon prop, a Nemesis/Spitfire would be a fun and low cost experiment. I think you should consider Merc's general recommendation and stay with the same pitch IF you are currently operating in the desired range with a standard prop (read 3-blade). Your motor might be OK with a 15p pontoon Spitfire, but would likely be in the low end of the desired RPM range. Don't know about you, but I would be a little disappointed with that...:)
 

Toddk9

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Thanks, that is what i am looking for. Other peoples experience. Maybe I will go with the Nemesis/Spitfire but a 13P first. Can use it as a back-up if i do not like it. I will call the PropGod guy and see what he recommends. I have a few months until spring anyway and would like to dial it in before it is 90's out.
 

basshawk84

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Thanks, that is what i am looking for. Other peoples experience. Maybe I will go with the Nemesis/Spitfire but a 13P first. Can use it as a back-up if i do not like it. I will call the PropGod guy and see what he recommends. I have a few months until spring anyway and would like to dial it in before it is 90's out.
I ran a Nemesis 13" when I had a 115 Yamaha 4 stroke on my Express Toon 22'. 6200 RPM, 31 mph, great hole shot and good handling around the dock.
 
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