How much of a pitch change do I need?

[Sea Rider]

A 16ft. G3 V167C marketed by the Yam Boat Company is a deep V aluminum boat that has nothing to do with an inflatable. Going back to the original post, have re propped many Tohatsu motors and some Yam ones, all the ones with factory delivered props were found extremely over propped running at wot around the min lugging rpm range which is a motor killer, usually needed 2 less pitch for motor to run towards the max wot rpm range while maintaining same diam and prop model.

Independetly of what the Prop Calculator says, need to tach current prop in a wot run as loaded as no one will ever suspect that props are being delivered way over propped and not best suited for your boat if top water performance is what you're after. have not seen so far any motor factory delivered with a prop being under propped.

Happy Boating

 

[Elkins45]

It’s an aluminum deep V fishing boat.

 

[WesNewell]

OK, the specs on this show 820# weight. Solas prop finder estimates 14P listing 13-15P props. Mercury prop finder estimates a 16p prop as in post 6. I run a 14P Solas ss prop on my boat that weighs 995# with 60hp 4s engine. If you are normally alone in boat, a 15P prop should be right with everything in good condition. In any case you should lose the whale tail. Get the engine mounted right and you won't need it or the drag it causes. If you go to a 4 blade go 1P lower. I still think the engine is too low in your photo.

 

[Elkins45]

820# is the dry hull weight. Add 190# for the motor, then 12 gallons of fuel, three batteries, my fishing gear and 250# for me.

 

[WesNewell]

OK, here it is. results are self explanatory, and why I said a 15P prop was the right prop. I included 12 gal of gas and 400# for people and gear. Now if you are at altitude, that could make a difference. Run it yourself.
[h=3]Your setup[/h]

• Boat type: Aluminum - Console
• Usage: Overall good performance/0 ft
• Engine Manufacturer:
  Yamaha
• Engine Type: Outboard
• Engine Year: 2003
• Number of Engines: One
• Engine Family: 3 Cyl 2-Stroke
• Engine: 50
• Drive / Gear Case: Yamaha 25-50 hp 2S, 40-60 hp 4S 1.85 Ratio

[h=3]Details[/h]

• Calculated Pitch: 15.54
• Calculated Weight with engine(s): 1,482.40 lbs
• Calculated Engine RPM: 5,000
• Calculated Boat Speed: 33.58 mph

 

[Faztbullet]

[No message]

 

[Sea Rider]

The Merc selector only recommends Merc/Solas whatever other prop brand they comercialize which has nothing to do as the OP's prop is a OEM Yam 15 pitch one. Buy same model prop with 13 pitch and continue your boating life or keep bitting your tails with posts going to Nowhereland any time soon...

Happy Boating

 

[WesNewell]

The Mercury prop selector only recommends Mercury props. It does not list any other prop brands. The pitch it calculates should apply to all brand of props, not just Mercury branded props. While different brands of props may perform differently, The calculations to arrive at a pitch are simple mathematics that don't care about who made the prop. A 15P prop of any brand will travel the same distance of any prop of the same pitch. That's 15 inches per revolution. It can't travel any more or less than that. Blade shape and rpm determines the amount of thrust provided.

 

[Elkins45]

Faztbullet, how did you generate that G3 data?

 

[Sea Rider]

The Mercury prop selector only recommends Mercury props. It does not list any other prop brands. The pitch it calculates should apply to all brand of props, not just Mercury branded props. While different brands of props may perform differently, The calculations to arrive at a pitch are simple mathematics that don't care about who made the prop. .

Really, very instructive tech info as usual. According to my experience max propping Yam motors in that HP range and higher to run towards its max wot rpm range, if you test an Yam OEM prop with a non one in same pitch, both will rev much different as the Merc is not the exact duplicate of the the Yam one.

Different 15 HP prop brand will not travel the same distance as prop shape, blade distance from hub, blade length and diam will account for that scenario not to happen, Iboats have some post of boaters regarding this issue, installed same prop pitch switching to other brand props and the water run was not near same of what was expected. If plan throwing all prop brands with same pitch in same sack and pretend to work exact same between them have flown long ago over the cuckoo's nest mate.

According to both posted charts, the latter is based on a 12 pitch prop, not a 15 one, assume the first one correspond to the water trial experienced with a 12 pitch at several motor rpm, speed, fuel consumption, if so, both charts are useless....

Happy Boating

 

[Faztbullet]

Those charts are from Yamaha from on water testing and recommended set up..Set motor in second hole, loose the K style prop and whale tail

 

[Cobe Marine]

This will let you know what should be used.
https://turningpointpropellers.com/PROPWIZARD/index.html?tan=

 

[Sea Rider]

This will let you know what should be used.
https://turningpointpropellers.com/PROPWIZARD/index.html?tan=

Sorry mate, the OP runs a 50 HP Yam motor with an OEM prop, he should prop right his motor with same OEM prop style, say a 13 pitch one, will work a zillion times better bumping the actual poor wot rpm way higher than what the Rule of Thumb states, how much ? only a wot water test will tell, theoretical data which dislike posting will be 100% pure speculation..

Without offence, don't tell me, don't care at all what other brand Prop Calculators suggests/recommends as always re prop my and my friend's motors with OEM props only, that's after a exhaustive wot water trial...

Happy Boating

 

[Elkins45]

This will let you know what should be used.
https://turningpointpropellers.com/PROPWIZARD/index.html?tan=

It recommends a 12 pitch. Every online prop calculator I have used recommends a 12 pitch.

 

[WesNewell]

Not here, but whatever. It's your money and boat. A 12P prop should max out your rpm limiter if your engine has one. If you are looking for max speed and fuel efficiency, then you need to mount the engine higher and get a higher pitch prop. If you are wantt to be able to make sharp turns at speed, then leave the engine mounted lower so it won't blow out in a sharp turn at speed. Personally I don't run my boat at high speed and make sharp turns.

 

[Sea Rider]

Every online prop calculator I have used recommends a 12 pitch.

If every on line prop calculator indicates so, why is it taking that long to go for one. How much wot rpm increase do you expect the motor to achieve going for a 12 pitch in any other brand prop as the Yam OEM crap prop has been already excluded and forum banned.

Isn't known if a 12 pitch prop will kick in the rev limiter or not, only a wot test will tell, if suspect go for a 13 pitch one..

Happy Boating

 

[Elkins45]

If every on line prop calculator indicates so, why is it taking that long to go for one. How much wot rpm increase do you expect the motor to achieve going for a 12 pitch in any other brand prop as the Yam OEM crap prop has been already excluded and forum banned.

Isn't known if a 12 pitch prop will kick in the rev limiter or not, only a wot test will tell, if suspect go for a 13 pitch one..

Happy Boating

It arrived today. We shall see if it’s the wrong choice, but since I wanted a spare prop it won’t be completely wasted money even if it’s not the optimal size.

 

[Sea Rider]

Congrats, will be interesting to see how much wot rpm will the motor gain going for a 12 pitch ptop. Which prop brand did you finally go for ?

Happy Boating

 

[Elkins45]

It’s a Michigan Wheel Apollo.

 

[Elkins45]

A follow up:

I finally had the chance to get my boat back out on the water with the 12 pitch prop replacing the 15. WOT increased from 4400 to 5100 rpm and I picked up somewhere around 2mph top speed. Prior to buying the new prop I had lifted the motor one hole and experienced blowouts in moderate turns at speed. I hadn’t moved it back down and experienced the same with the new prop. I have now moved it back down to the original lowest position and will test it again to see if I lose any of my new 2mph gain in exchange for regaining my steering stability.