Would a prop too thin..

mnm99

Seaman Apprentice
Joined
Nov 5, 2014
Messages
33
cause more flex resulting in more or less rpm? If a prop was redone too many times and was getting thin on the blade side. Thanks
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
A prop shop worth its salt measures blade thickness
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
I had an OEM aluminum prop on a 1972 Johnson 125 back in 1972 that got a trip to the prop shop every Monday after a weekend on the water for its first summer.....before I bought an OMC SST (Stainless Steel Teflon...coated). I didn't notice any reduction in performance over the summer on an 18' boat which pulled a lot of skis.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Just curious, this blade flexing is something that's been technically corroborated by prop manufacturers on water tests on laboratory, word of mouth, whichever. Assume too much flexing will produce prop vibrations at speed, lose of best blade grip on water along less rpm ? The higher the HP, the thicker blade will be if are aluminum built.

Happy Boating
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
Blade flex, the term has been very successfully marketed to sell a lot of SS props.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
I'm not a propulsion engineer so I don't know the "bending moment" of certain cast aluminums nor the resistance to thrust offered by water to props attempting to turn in water but this is a fact. Turning Point Hustler put a lot of technology in their props. I have one. The thing that they don't have in their alum. props is stainless steel. However, they do have their own special formula/process that produces a rigid aluminum that allows them to make their blades thinner than the norm thus getting as close as they can to SS without the cost. All their amenities in their props are readily available on the www.

So, apparently there is something to aluminum blades bending under high load factors.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Read somewhere that SS props are only good for + 40-45 MPH speeds, so useless on much less powered OB's that runs say 20-35 MPH.

Happy Boating
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
Turning Point Hustler put a lot of technology in their props.

So has Mercury and BRP.

I have handled several TP props and have noticed their Quality Control to be lacking. Several props had a change in the rake angle midway up one blade.

People will buy the aftermarket brands because they are cheaper, and because they see/hear advertisements that the prop is better. I myself have never gotten better performance from an aftermarket prop than what I attained from Merc or OMC/BRP props
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
So has Mercury and BRP.

I have handled several TP props and have noticed their Quality Control to be lacking. Several props had a change in the rake angle midway up one blade.

People will buy the aftermarket brands because they are cheaper, and because they see/hear advertisements that the prop is better. I myself have never gotten better performance from an aftermarket prop than what I attained from Merc or OMC/BRP props

Well sir you don't have to take a back seat to anybody. Your Avatar says it all. Care to say what your numbers were when that picture was snapped? Light chop, not crossing a wake (don't see any)?
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
That pic was taken 5 or 6 years ago so I can't recall any specifics(my cousin was driving) other than the prop is a 20in Enertia.
Here the pic a bit bigger and one before it DSC_1000a.jpg



0.60 seconds later, my avatar shot DSC_1002c.jpg
 
Last edited:

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
That pic was taken 5 or 6 years ago so I can't recall any specifics(my cousin was driving) other than the prop is a 20in Enertia.
Here the pic a bit bigger and one before it



0.60 seconds later, my avatar shot

(Moderator, we're waiting on originator of post, not stealing his thread) Really nice for a rig that size; I/O at that. What's your mil and mph?
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
VP 5.7. Speedo quits at 55mph, but needle continues till it is pegged, the engine is not at peak rpm when speedo is pinned. Other boats who have paced me say It goes a bit over 60. With a 4bbl on it, the rpms increased about 10%, so I had to go to a higher pitch prop and it did go faster, as the speedo pinned at a lower rpm but the top rpm was still about 100 higher than with the 2bbl. I would guess it goes about 66 with the 4bbl
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
VP 5.7. Speedo quits at 55mph, but needle continues till it is pegged, the engine is not at peak rpm when speedo is pinned. Other boats who have paced me say It goes a bit over 60. With a 4bbl on it, the rpms increased about 10%, so I had to go to a higher pitch prop and it did go faster, as the speedo pinned at a lower rpm but the top rpm was still about 100 higher than with the 2bbl. I would guess it goes about 66 with the 4bbl

I believe it with no more hull than you have in the water and with the deep V it's like you are "on the pad". Glastron is a fine hull. I used to live in Austin where they were originally made back in the '60's.
 
Top