Prop pitch suggestion for 2019 Yamaha vmax 90 sho

8pt172

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Jun 30, 2019
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I am re-powering my 16.5' aluminum mod v boat with 88" beam(1000 lbs empty) from a 70hp with 2.15 gear to the 90 sho with a 2.33 gear. Currently I am running a 13.5" x 15 aluminum and am getting to 6200 at full throttle and trimmed up. From looking at the Yamaha prop selector, they suggest 3 different pitches, 18, 19, and 20 on the Talon SS.

Anyone running the new Yamaha 90 sho on a similar size boat? I was thinking going with the 19 pitch.
 

WesNewell

Chief Petty Officer
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Jan 3, 2018
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497
IF you have the engine mounted at the proper height, you should be running a 23P prop and turning ~5500 rpm @47 mph. That's with 500# people and gear and 20 gal of fuel. A 19p would be rec. for 1050# people and gear.
 

8pt172

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Jun 30, 2019
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Just picked up my boat and started the break in period. I am into the 2nd hour and am running 27 mph @ 4000 rpm with 19 pitch SS prop. What speed can I realistically expect when I hit WOT and hopefully ~ 5900 rpm. Is there any calculation that can estimate it?
 

Sea Rider

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Sep 20, 2008
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Why do you run the motor trimmed up, don't know if fully though ? Combo should run parallel to water level once on plane, usually having motor set at 0 (neutral) trim as in pic. Distribute deck load evenly and try (1) setting.

Possible Trim Angles.JPG

Any motor trimmed up will achieve a bow up condition, will make driver to lose front sight on what's going on at bow, too much hull bouncing on choppy, rough water cond and excessive lower leg drag if happens to count with a added doel fin.

Happy Boating
 

Faztbullet

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Mar 2, 2008
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15,589
You use trim to get maximum amount of boat out of the water. The less wetted surface the faster you go and ride is better...it all depends on hull. 90° is not correct anymore except on non pad boats, 70-80° works best with the newer hulls. Below is pic of pad style aluminum boat at proper trim.....
Image result for gator trax bass boat
 

8pt172

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Jun 30, 2019
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you're running a 13% slip now. keeping that the same @5900rpm you should see 40 mph.
https://www.go-fast.com/Prop_Slip_Calculator.htm

I finished the 2nd hour and am now opening it up on short runs. I am able to reach 5900 rpm with some trim up with 2 people and 1/2 tank. My GPS read 41.9 mph. The water wasn't flat and there was a nice cross breeze. I anticipate running over 42 with flat conditions and maybe a little quicker by myself. Looks like I picked the right pitch for running 2-3 people.

Thanks for the responses!!
 

Sea Rider

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You use trim to get maximum amount of boat out of the water. ]

Touche with that, but once combo is on plane should trim motor as in the pic example to run parallel to water level, works best on all water cond from flat calm to windy and choppy sea conditions as well. On manual trim motors trim should be left at 90 deg as it's impossible to vary the trim angle.

You can't possibly compare and put in same sack a 200 HP with newer hull as in pic against OP's older combo and less than half HP of his current motor. Would like to see that prime example ridding full wot under rough water cond on open waters, not on a lake, calm river, stuary whichever that combo was shot at and at a non other than a straight water course.

Speed solo boating has nothing to do with Recreational Family Oriented Boating, to each their own boating settings, parameters and lboating preferences. BTW, the posted trim chart was excerpted from a 300 HP motor, Owner's Manual.

Happy Boating
 

Faztbullet

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once combo is on plane should trim motor as in the pic example to run parallel to water level, works best on all water cond from flat calm to windy and choppy sea conditions as well.
That nonsense as if I ran my boat this way it would get maybe 55MPH...using trim it gets to over 70MPH. You must not have fast or pad hulls where you are at...
You can't possibly compare and put in same sack a 200 HP with newer hull as in pic against OP's older combo and less than half HP of his current motor.
Co-owned a 20ft Lowe Jon boat with 115 TOP with jack plate tha ran 40+MPH with 2 dogs,3 men and about 500lbs of decoys and camo netting and this does closly compare to OP's rig. Also whos manual as no mfg I know use cartoons in a manual....
Hey 8pt....told ya it would be close.After break in take prop to a propshop and have a cup added to trailing edge,will reduce RPM about 150 and make prop bite better adding maybe a MPH
 

QBhoy

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Mar 10, 2016
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8,286
Touche with that, but once combo is on plane should trim motor as in the pic example to run parallel to water level, works best on all water cond from flat calm to windy and choppy sea conditions as well. On manual trim motors trim should be left at 90 deg as it's impossible to vary the trim angle.

You can't possibly compare and put in same sack a 200 HP with newer hull as in pic against OP's older combo and less than half HP of his current motor. Would like to see that prime example ridding full wot under rough water cond on open waters, not on a lake, calm river, stuary whichever that combo was shot at and at a non other than a straight water course.

Speed solo boating has nothing to do with Recreational Family Oriented Boating, to each their own boating settings, parameters and lboating preferences. BTW, the posted trim chart was excerpted from a 300 HP motor, Owner's Manual.

Happy Boating

Hi

Are you seriously saying that running like the boat in the picture is what to do in all conditions ? Maybe I’ve picked you up wrong.
 

Faztbullet

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Mar 2, 2008
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Lets just say Qboy you wouldn't like riding with me !!!!!!
When in Doubt – Trim it Out
fastboat.jpg.png

 
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Sea Rider

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Sep 20, 2008
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Faz, no one is interested on the improvements and achievements you have managed to get out of your combo, each combo and the type of boating each boater likes doing it's personal. Will allow myself to remaind you that Recreational Boating has nothing to do with Speed Crazy Boating you love doing. .

Nope, I'm not in favour of running that way and putting my precious life in jeopardy, only good for cracy boaters running their combos at speed on calm water cond at straight water courses speeding direct to Bimin. Running at such speed if you're not a experienced or skilled boater can turn into a candidate for serious water disaster.

A combo at that speed running with hull 90% out of the water will achieve a nervous behaviour water ride, it's like riding a motorcycle at speed on rear wheel on a straight road with 0 steering capability if in need of a fast evasive maneuver. Same lag maneuver applies here when in need to change direction fast, at a near collision with other boat or whatever puts your life in jeopardy while boating.

As this will turn into another endless and useless discussion with you and my boating time is precious will end saying, : To each his own way of boating and voila!!

Happy Boating
 

Texasmark

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Dec 20, 2005
Messages
14,544
you're running a 13% slip now. keeping that the same @5900rpm you should see 40 mph.
https://www.go-fast.com/Prop_Slip_Calculator.htm

Darn.....you beat me to it!

On your 4000 RPM operation expect your prop slip to be a few numbers higher since more of the boat will be in the water and your drag will be higher there..... which will skew your answer somewhat. Like figure a 12% slip at WOT and maybe 15% or more at 4000.
 

Texasmark

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Dec 20, 2005
Messages
14,544
Why do you run the motor trimmed up, don't know if fully though ? Combo should run parallel to water level once on plane, usually having motor set at 0 (neutral) trim as in pic. Distribute deck load evenly and try (1) setting.



Any motor trimmed up will achieve a bow up condition, will make driver to lose front sight on what's going on at bow, too much hull bouncing on choppy, rough water cond and excessive lower leg drag if happens to count with a added doel fin.

Happy Boating

Try running a Bass Boat with a Pad (flat area where the keel is supposed to be,liken to a water ski) and put an engine behind it that has enough whoopie to get you up on it and away....it's called "bow lift" and has nothing whatsoever to do with your pictures......your pictures are made for the boats you like to run.....per your signature....proud smoking Tohatsus 30 hp max.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
I am re-powering my 16.5' aluminum mod v boat with 88" beam(1000 lbs empty) from a 70hp with 2.15 gear to the 90 sho with a 2.33 gear. Currently I am running a 13.5" x 15 aluminum and am getting to 6200 at full throttle and trimmed up. From looking at the Yamaha prop selector, they suggest 3 different pitches, 18, 19, and 20 on the Talon SS.

Anyone running the new Yamaha 90 sho on a similar size boat? I was thinking going with the 19 pitch.

My avatar was my 2002 Merc 90 2 stroker at 2.33 also, me alone, running 5700-5900 RPM, 171/2' stepped alum hull, Ballistic 24XL kissing 50 GPS (Explorer model GPS). It never would have happened with an alum prop, even a Turning Point Hustler as I tried one once and it didn't make the grade. Only difference I can see is the yammie is about ⅔ the cubes of my Merc and turns about the same rpms, per the data sheet. Since cubes usually support torque and torque is ½ the HP equation I don't see how they get their 90 hp....but apparently they do so you should get the same results. But you change anything and the 19 should be your better bet.
 
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