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midwestfisher

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Folks, have a 2005 Johnson 115hp 4 stroke motor.
Need a prop and have no clue what to do as the manual is of no help.
There are three numbers on the existing prop (see pics). Want to stay with aluminum though.
You all have helped in the past which I greatly appreciate and this is above my pay grade and what to ask on Google.
What are these and can the tell me what to get? Thanks in advanced
 

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LDUBS said:
"13.75x17" = 13.75 diameter x 17 pitch.

"778739" must be a model number. Put that in google and it returns a 4 blade 13.75x17 prop.

No idea what the "21 15" means.
Click to expand...

That with your engine model/year to ID the hub/splines and gear case diameter should get you there.

I have had good luck with Solas aluminum replacement props.
 
Last edited:
Is this current prop operating properly for you ? If a change is needed, now would be the time.your engine should be reaching max rated RPM at wot..if not make adjustments on the replacement prop.
 
LDUBS said:
"13.75x17" = 13.75 diameter x 17 pitch.

"778739" must be a model number. Put that in google and it returns a 4 blade 13.75x17 prop.

No idea what the "21 15" means.
Click to expand...
Well you are correct that is the model number. Now after calling a boat service person the part is no longer made. I can't get this anymore. Gave me some other manufacturers of props that could have an aftermarket unit. So....now what? Crazy there has to be a ton of Johnson's still out there.
 
midwestfisher said:
Well you are correct that is the model number. Now after calling a boat service person the part is no longer made. I can't get this anymore. Gave me some other manufacturers of props that could have an aftermarket unit. So....now what? Crazy there has to be a ton of Johnson's still out there.
Click to expand...

@FuzzyGrub mentioned Solas in his post above. I would go to them for a replacement. I guess it would be aftermarket but I would consider them reputable and wouldn't worry about getting poor quality from them.

Go to the Solas Prop Finder. Enter your part number (778739). You will get a direct hit on a replacement prop. Once you have the Solas part number, you can shop online or have your local guy order one up.

BTW, I recently bought a new prop for my Honda motor. Says Honda in big letters on the box but is actually made by Solas.
 
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Th
LDUBS said:
@FuzzyGrub mentioned Solas in his post above. I would go to them for a replacement. I guess it would be aftermarket but I would consider them reputable and wouldn't worry about getting poor quality from them.

Go to the Solas Prop Finder. Enter your part number (778739). You will get a direct hit on a replacement prop. Once you have the Solas part number, you can shop online or have your local guy order one up.

BTW, I recently bought a new prop for my Honda motor. Says Honda in big letters on the box but is actually made by Solas.
Click to expand...
anks
LDUBS said:
@FuzzyGrub mentioned Solas in his post above. I would go to them for a replacement. I guess it would be aftermarket but I would consider them reputable and wouldn't worry about getting poor quality from them.

Go to the Solas Prop Finder. Enter your part number (778739). You will get a direct hit on a replacement prop. Once you have the Solas part number, you can shop online or have your local guy order one up.

BTW, I recently bought a new prop for my Honda motor. Says Honda in big letters on the box but is actually made by Solas.
Click to expand...
Thanks, have reached out to Solas. Have you ever heard of Turning point Props or Michigan Wheel? These were 2 of the ideas the boat repair guy suggested as well.
 
midwestfisher said:
Th

anks

Thanks, have reached out to Solas. Have you ever heard of Turning point Props or Michigan Wheel? These were 2 of the ideas the boat repair guy suggested as well.
Click to expand...
I’ve had both of those brands in I/O props. They work. I think Solas has a wider selection.
 
I think all three of these brands have been recommended at one time or another in these forums. I am far from an expert, but feel all of them are bonafide brands. Meaning I guess you wont go wrong choosing among them.
 
Most folks get hung up on the diameter and that is where a lot of confusion comes in. Pay more attention to the pitch number. This is the bare minimum K.I.S.S. method and for the most part.......it works.
Diameter and the number of blades gains importance when the application deviates from the norm (typical fishing or pleasure application). Pontoons, larger heavier hulls with the minimum HP, non-planing, etc can benefit greatly from taking advantage of diameter. To keep this in perspective keep in mind that if you want to move a larger heavier load then you need to move a large (diameter) column of water at a slower speed. LIghter, faster applications benefit from moving a smaller (diameter) columm of water at a higher speed.
More extreme applications (non planing)require looking for propellers with a high DAR or Disc Area Ratio which is a more common term for inboard/V-drive boats in which the area of each blade, the design, and the number of blades and the percentage of the rotational dixc that is covered by the blades is looked at.

For our average applications.....look at the pitch number and occasionally the number of blades and go on with life!
 
Crazyboat said:
What kind of boat do you have that you use a 4 blade prop? Most engines in that HP range use 3 blade props? Max RPM with light load.
Click to expand...
In general a 4-bl prop will get you on plane a bit quicker and provide better slippage rates up through mid-range RPMs (fuel economy) and hang in a bit better through corners at the expense of giving up a bit of speed at WOT. All of this depends on YOUR set up.
 
Pappy said:
In general a 4-bl prop will get you on plane a bit quicker and provide better slippage rates up through mid-range RPMs (fuel economy) and hang in a bit better through corners at the expense of giving up a bit of speed at WOT. All of this depends on YOUR set up.
Click to expand...
Why are you telling me this?
 
Pappy explained it well, and is sharing information for all reading, not just you.

Since you asked about 4 blade prop use, he used your reply to share the general characteristics of 4 blade vs 3 blade.

Don't get crazy, Crazyboat! 🤪
 

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