How do chips in the propeller affect performance?

[Seanmccullar]

You can see my 1958 Johnson RDE-19 propeller has a few nicks. When should a propeller be replaced?

 

[Scott Danforth]

Get it repaired

 

[F_R]

That prop looks like new, compared to some oyster bed dredges I've seen around here. How picky are you concerning performance? Sure, you might lose one MPH, but you will never be able to notice it.

 

[Chrisravosa36]

I boats has one of the best propeller guides around, I looked up your prop and they have a few diffrent pitches for it, about 70$. That looks good to me though, but its nice to have a new one, then a spare.

 

[fhhuber]

Each chip/nick/ding has SOME negative effect adding drag and turbulating the flow over the blade. Also the missing (in the case of chips/nicks) metal can unbalance the prop .Best is a clean shiny new looking prop.

Its a question of when the damage is sufficient to warrant the repair or replacement for your purpose. A racer is going to want that bright shiny new looking prop.

Yours is at a point where I'd get it fixed/replaced if it were mine. Others might consider it just getting broken in. Its still good for a spare in case you hit a stump and break a blade on the replacement.

 

[bruceb58]

Besides the performance, just the fact that your prop is likely VERY out of balance is enough reason to get it repaired.

 

[boobie]

Agree with the above with the out of balance. You may not feel it but that prop is setting up vibrations through out that motor which is not good.

 

[bob johnson]

when they get like this performance suffers a little..... my 115 ocean runner could only push the boat about 4 mph with this prop on it!!!

 

[oldboat1]

Ha! In theory, think the most efficient prop would be a single bladed one. So bob johnson's prop is right up there in efficiency.

Think the OP's prop is in decent shape (even with that less efficient three blades....!) I've cleaned up nicked up props with a grinder and sander -- think the prop pictured could be tweaked and used (MO).

 

[fhhuber]

Well... the single blade is most efficient on an aircraft... but the dynamic load imbalance is hell on the bearings, even if you get the static balance right.

Not sure about boat props but I suspect it would be similar. The tip of the prop is a major contributor to drag (power demand).

Yes, the OP prop could be ground to being even, rebalanced and be just fine. A little less load on the motor (and a little less top speed) due to loss of blade area.

 

[Seanmccullar]

This funny! Thanks for all of the advice! I am a first time boat builder (glen l zip) and also a first time engine rebuilder, so some of my questions are actually very comical in retrospect. I appreciate the forum!
I think I will repair the blade, save some cash and forgo 1 hp in performance!

 

[fhhuber]

Watch Craigslist... you can find some decent props for low cost.

It IS a good idea to have a spare. Undersize (pitch and/or diameter) is preferred vs oversize as long as it properly fits the shaft. something to get you home if your prop suddenly looks like

 

[Chrisravosa36]

Watch Craigslist... you can find some decent props for low cost.

It IS a good idea to have a spare. Undersize (pitch and/or diameter) is preferred vs oversize as long as it properly fits the shaft. something to get you home if your prop suddenly looks like

A little grinding and welding and this prop will be like new :lol:

 

[bruceb58]

I think I will repair the blade, save some cash and forgo 1 hp in performance!

You will get to repair your lower unit when your bearings wear out from running an out of balanced prop!

 

[fhhuber]

If you don't have experience balancing props... Probably best to get help.

all of the props I've balanced... it would no problem for me to grind the blades even then balance it. I have a balancer that is accurate enough to balance a 6-32 nut.

 

[Seanmccullar]

good point :facepalm:

 

[jimmbo]

No Title

I too have a one blader