How Shot Is My Propeller?

[Makaw]

Here’s the original propeller for my 1967 Johnson 20 hp model FD-21r, so it’s seen it’s fair share of water, mud, sand, debris..., as is evident in the photos.

How bad is it? Am I losing significant performance from the dings and bent sections? Will it help if I remove the burrs and minimize bent areas? Or is it past the point of being worth using?

Mainly asking to see how much of a priority I need to make a prop upgrade as I restore the boat (A. Upgrade asap! B. Meh, run it for a year and upgrade next winter! C. Nothing needed, it’s good for another 63 years!). Being a 9X9 pin-drive, my options seem quite limited. Would take general prop suggestions as well.

Some additional info if it’s helpful:
Boat is a 70’s era 14’ Starcraft side console. I haven’t driven in 10+ years, so no memory as to boat performance. Current upgrades are adding between 150-200 lbs of mid/forward weight, not including operator (185 lbs). Will mainly be using solo, but occasionally with 2nd adult. No idea on max rpm, other than I have a snippet from an old Johnson service manual stating 20 hp is produced at 4,500 rpm (I think this is simply a power curve reference, not related to max rpm). Manual also states idle speed in gear should be 550 rpm. No real concerns about top speed, more concerned about overall performance and holeshot, especially since I’m adding weight to the boat.

Photos below show current condition of prop. Johnson part #311484.

 

[ktoelke54]

I’d replace it. When they get that chewed up, my concern is not only loosing power, burning more fuel, but also out of balance vibration and the extra stress it places on the lower unit.


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[Piomarine]

I’d look around for a place that will do prop repair. On my 57 sportwin I was missing a silver dollar sized chunk of the prop, and they get some new metal welded on and made that prop look factory new! And did it for half the cost of a new prop. It cost me $32 for the repair at a small prop shop here in Fort Worth.


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[CedarRiverScooter]

Buy new & use that one for a limp home spare. The repair weld is not as good as virgin material.

 

[Piomarine]

I agree but the only things you would do to compromise the weld are things that you probably shouldn’t be doing with a boat to begin with. I will take the cost of a tig weld repair over new if I can avoid it. Me and my dad have been using repaired props for decades without ever having an issue.


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[maintenanceguy]

I just replaced one that looked almost exactly like yours. I'm glad I replaced it because cracks start at edge damage and I don't want to lose a blade or a chunk of a blade while I'm on the water. But I haven't noticed any difference in performance. Same hole shot, same top end.

 

[RaisedByWolves]

I’ve seen and fixed a lot worse.

 

[overboard]

Plenty of props on boats used on rivers that look like that and worse.
That prop isn't really that bad, touch it up a bit and use it, or touch it up a bit, buy a new one, and then keep it as a spare.
I've had props that look like that and just filed off the burrs on the edges without a problem, be careful if you try to straighten any major dents as it may crack, minor ones I never had a problem doing it.

 

[Makaw]

Thanks all for the helpful feedback! I had not considered having the prop repaired - living in Michigan close to Lake Huron I'm sure it wouldn't be hard to find someone in my general vicinity that performs that service. I like to tinker... but it's probably better that I don't try to mend the bent areas if it will run the possibility of fracturing the aluminum. Keeping my original as a backup replacement sounds like a wise idea as I'll be running this on new-to-me lakes and rivers. Solas has the only brand new prop replacement (that I'm aware of), but it runs a different pitch. Maybe down the road I'd test a 10" pitch, but for now I'd like to stick with 9" to get a performance baseline. OEM replacements can be found on eBay, but are fairly pricey and I'd venture to guess that most are repaired props.

 

[overboard]

My one buddy slightly banged up the prop on his bass boat on the river, he bought a brand new one, installed it, and on the first trip back to the river, while backing the boat out in reverse, he banged up the new prop when he hit a rock. Lesson learned, use the old slightly banged up prop on the river and then install the new one for use on the lakes when he went to Canada, doesn't take long to switch props.

 

[MrGiggles]

Thanks all for the helpful feedback! I had not considered having the prop repaired - living in Michigan close to Lake Huron I'm sure it wouldn't be hard to find someone in my general vicinity that performs that service. I like to tinker... but it's probably better that I don't try to mend the bent areas if it will run the possibility of fracturing the aluminum. Keeping my original as a backup replacement sounds like a wise idea as I'll be running this on new-to-me lakes and rivers. Solas has the only brand new prop replacement (that I'm aware of), but it runs a different pitch. Maybe down the road I'd test a 10" pitch, but for now I'd like to stick with 9" to get a performance baseline. OEM replacements can be found on eBay, but are fairly pricey and I'd venture to guess that most are repaired props.

Most don't repair aluminum props, they are just too cheap, unless getting a replacement is difficult.

 

[wrench55369]

Here’s the original propeller for my 1967 Johnson 20 hp model FD-21r, so it’s seen it’s fair share of water, mud, sand, debris..., as is evident in the photos.

How bad is it? Am I losing significant performance from the dings and bent sections? Will it help if I remove the burrs and minimize bent areas? Or is it past the point of being worth using?

Mainly asking to see how much of a priority I need to make a prop upgrade as I restore the boat (A. Upgrade asap! B. Meh, run it for a year and upgrade next winter! C. Nothing needed, it’s good for another 63 years!). Being a 9X9 pin-drive, my options seem quite limited. Would take general prop suggestions as well.

Some additional info if it’s helpful:
Boat is a 70’s era 14’ Starcraft side console. I haven’t driven in 10+ years, so no memory as to boat performance. Current upgrades are adding between 150-200 lbs of mid/forward weight, not including operator (185 lbs). Will mainly be using solo, but occasionally with 2nd adult. No idea on max rpm, other than I have a snippet from an old Johnson service manual stating 20 hp is produced at 4,500 rpm (I think this is simply a power curve reference, not related to max rpm). Manual also states idle speed in gear should be 550 rpm. No real concerns about top speed, more concerned about overall performance and holeshot, especially since I’m adding weight to the boat.

Photos below show current condition of prop. Johnson part #311484.

Try Soderbloom in Wright,MN. They offer a flat fee for repairs and have done right by me several times. :wink: