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Kennneee

Propeller Advice

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Hi Guys- I pulled the trigger and purchased a new Yamaha VF90SHO for the Outer Banks 26 that I am building.  This is the first of the design and this is a new model motor from Yamaha.  The motor has a lower unit gear ratio of 2.38:1.  The salesman claims this motor puts out almost 115 hp but I am not sure he really knows.  When I call Yamaha Tech Help the agent reads the brochure to me and really hasn't had any real life experience with this motor. The OB26 should weigh somewhere between a BJ25.5 and a BJ28. Wondering if you could offer any advice on propeller sizing and type. Thanks!

Ken

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Good Evening Ken.. I went thru several Props before I settled on a 14inch 13 degree prop after trying several different pitches.. As the Yamaha propeller chart does not cover boats of our length for the 90 hp it is a roll of the dice.  The company that put the motor on had only one prop to try and that was a 15 pitch.. that did not allow the motor to reach red line rev. at 6ooo.  it would get up to 5500.  I then tried a 11 pitch.. and that allowed the motor to go over the 6000 mark and shut down.. I then tried a 4 blade 13 pitch prop which has done what was expected.  Best info that I can offer.. and keep me in the loop on that motor.. I am interested.  

 

Side note .. I will be in the Vancouver area The middle of August 2019. Would like to catch up with you and see your build.. 

Henry

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Ken,

 

In a few short weeks I'll be buying a prop for my Bluejacket 25.5  with a Yamaha F70.  I'm clueless how (with great confidence) one can start with boat and engine data points and convert these into prop pitch,  diameter and number of blades to achieve a desired level of performance.  

 

My boat's sistership with a Yamaha F70 uses a Solas 3431-140-11 prop:  14D X 11pitch  and three blades.  In the absence of a better recommendation I'll look for an aluminum prop with these design specs.  Since you have a different engine with no doubt different gearing, this prop information is probably useless to  you so I offer it for entertainment purposes only.  

 

Within days of launching his Bluejacket 27', my friend Ed bought a replacement prop for his Honda 60 hoping to achieve greater top speed.  Perhaps the right prop is only found after dropping a couple of hundred $$ here and there on a trial and error prop search.  

 

My boat is at a dealer having the Yamaha installed.  I told the service manager of my belief that an aluminum prop for a non-high performance midsize outboard boat is best in order to save the lower unit when a prop strike occurs (blade breaks off thus acts as a fuse).  Thought I was gonna start  a debate but he said that a steel prop should not be used on an outboard of less than 150 hp because the lower units are not beefy enough to substain  the shock damage when a steel blade stays intact after a prop strike.    My boat's playground will be Lake Travis, Tx with its many limestone ledges.  

 

No doubt those with 40 knot Bass boats  think I'm nuts to install a cheapo aluminum prop which can distort under load and perhaps cost my W.O.T 25 knot Bluejacket  perhaps a knot in top  speed.  

 

If I'm wrong about my aluminum versus steel propeller beliefs,  I look forward to being corrected by those with real life experience before I purchase my prop. 

 

 

 

 

 

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12 minutes ago, DaveH said:

Ken,

 

In a few short weeks I'll be buying a prop for my Bluejacket 25.5  with a Yamaha F70.  I'm clueless how (with great confidence) one can start with boat and engine data points and convert these into prop pitch,  diameter and number of blades to achieve a desired level of performance.  

 

My boat's sistership with a Yamaha F70 uses a Solas 3431-140-11 prop:  14D X 11pitch  and three blades.  In the absence of a better recommendation I'll look for an aluminum prop with these design specs.  Since you have a different engine with no doubt different gearing, this prop information is probably useless to  you so I offer it for entertainment purposes only.  

 

Within days of launching his Bluejacket 27', my friend Ed bought a replacement prop for his Honda 60 hoping to achieve greater top speed.  Perhaps the right prop is only found after dropping a couple of hundred $$ here and there on a trial and error prop search.  

 

My boat is at a dealer having the Yamaha installed.  I told the service manager of my belief that an aluminum prop for a non-high performance midsize outboard boat is best in order to save the lower unit when a prop strike occurs (blade breaks off thus acts as a fuse).  Thought I was gonna start  a debate but he said that a steel prop should not be used on an outboard of less than 150 hp because the lower units are not beefy enough to substain  the shock damage when a steel blade stays intact after a prop strike.    My boat's playground will be Lake Travis, Tx with its many limestone ledges.  

 

No doubt those with 40 knot Bass boats  think I'm nuts to install a cheapo aluminum prop which can distort under load and perhaps cost my W.O.T 25 knot Bluejacket  perhaps a knot in top  speed.  

 

If I'm wrong about my aluminum versus steel propeller beliefs,  I look forward to being corrected by those with real life experience before I purchase my prop. 

 

 

 

 

 

I have no problems running an aluminum prop. But lately the Solas props are a crap shoot as it relates to dependability of their pitches being as stamped. Currently I am using a Powertech, which are pretty reasonable. I picked it up for 110 bucks, brand new. I am using it on my 115 now and ran it today after trying a stainless steel one that a good friend had and would not be using it. I am with you on favoring the aluminum over the SS for our uses.

 

 

 Sometimes a prop shop will have some used wheels that they will let you try. Some of the boat dealers that sells new boats will have wheels that they have tried on certain engines and boats and you can buy them fairly reasonable, even allowing you to try the gently used ones that they have themselves put on for a sea trial or two.

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